docs: absorb #174 and advance the anchors to 0442d78

#174 merged while this PR was open, so the lane it had just been given
is already a merged lane. Rule 4 removes those rather than relabelling
them — but only once the durable facts are in the handoff, so do both
here in that order.

docs/agent-handoff.md
- §5 gains the lesson: a wait predicate WEAKER than the assertion it
  guards is a race on whichever platform loses it, and "wait until the
  file mentions X, then assert Y" races whenever Y is stricter than X.
- Two things that generalize past the fix ride with it: a race you
  cannot reproduce can still be bitten at one remove (an unsatisfiable
  predicate proves the wait is load-bearing; the old predicate still
  passing proves a local run cannot tell them apart), and the obvious
  fix is sometimes worse — the sibling m4_26 is deliberately left alone
  because closing it the easy way trades a precise assertion diff for a
  vague five-second hang.
- Header and §1 anchor advance to 0442d78, noting #174 is test-only and
  #184 remains the substantive change at that head.

docs/active-work.md
- Remove the #174 lane; the header paragraph now says where it went.
- Canonical base and recovery floor advance to 0442d78. The floor
  explicitly rejects 6bee09d as well as 7fd646d, per its own rule that a
  check accepting an older commit than the declared base passes on a
  tree the file does not describe.
- Bottom-panel lane: 2B-2 is IN FLIGHT, not merely "next" — branch,
  worktree, and the fact it is branched fresh rather than stacked. Its
  boundaries are restated because they are easy to overrun: production
  Hello stays v20, panel_capable stays false, and 2B-3 may not simply
  bump the unsolicited Hello.
- dired lane: the re-scout is under way on the existing branch, so #171
  keeps its three-round history and the product is a rev 5.
- Both lanes note that main advancing to 0442d78 changes nothing for
  them, since #174 is test-only.

The bottom-panel framing doc keeps its 6bee09d ground-truth line: that
is a scouting statement about what was actually read, and re-anchoring
it to a commit nobody re-scouted against would be a false claim.

docs/active-work.md

@@ -21,11 +21,13 @@ number appears in `git log --first-parent githubsucks/main`, it has
 landed regardless of what a lane says.
 
 **Two open PRs had no lane here at all before this snapshot** — #174 and
-#171 — and both now have one. An open PR is exactly the volatile work
-this file exists to record, so its absence is a ledger defect rather
-than a tidy omission: #171 drifted **153 commits** while invisible here,
-and its still-green old CI run describes a tree nobody has looked at
-since. When a PR is opened, give it a lane.
+#171. An open PR is exactly the volatile work this file exists to
+record, so its absence is a ledger defect rather than a tidy omission:
+#171 drifted **153 commits** while invisible here, and its still-green
+old CI run describes a tree nobody has looked at since. **When a PR is
+opened, give it a lane.** #174 has since merged, so per rule 4 its lane
+is gone again and its durable lesson is in `docs/agent-handoff.md` §5;
+#171's lane is below.
 
 ## Repository authority
 
@@ -36,14 +38,16 @@ since. When a PR is opened, give it a lane.
   machine-local: `origin` may name this canonical URL, a release mirror,
   or something else, and therefore has no authority by name alone.
 - Canonical base at this snapshot:
-  `githubsucks/main` @ `6bee09d` (bottom-panel Stage 2B-1 #184, atop the
-  Journey/GPU directory-target ratchet #183, Journey Stage 1a #182 and
-  the previously recorded landed work). **Protocol schema support is
+  `githubsucks/main` @ `0442d78` (the M4 config-sink race fix #174, atop
+  bottom-panel Stage 2B-1 #184, the Journey/GPU directory-target ratchet
+  #183, Journey Stage 1a #182 and the previously recorded landed work).
+  **Protocol schema support is
   `v6..=v21`; the production server-first `Hello` still advertises
   v20** — two different facts, and #184 landed only the first. The
   previous snapshot named `7fd646d`, and **the
   recovery floor advances with it**: the check below now requires
-  `6bee09d` or newer, so a tree at `7fd646d` no longer passes. That is
+  `0442d78` or newer, so a tree at `7fd646d` — or at `6bee09d` — no
+  longer passes. That is
   deliberate — the floor moves with the base, because a check that
   accepts an older commit than the declared base passes on a tree the
   rest of this file does not describe.
@@ -82,7 +86,7 @@ git worktree list
 git status --short --branch
 ```
 
-The `git log` command must expose `6bee09d` — the base named above — or a
+The `git log` command must expose `0442d78` — the base named above — or a
 newer intentional main. Keep this threshold and the canonical-base line in
 step: a recovery check that accepts an older commit than the base it
 declares canonical will pass on a tree the rest of this file does not
@@ -224,15 +228,24 @@ If it does not, stop and repair the remote/fetch configuration.
   never been enforced. Any CI job that compiles the `crdt` targets has to
   fix them first or it will be red on arrival.
 
-## Bottom-panel lane (Arc 7) — 2B-1 MERGED; 2B-2 IS THE NEXT SLICE
+## Bottom-panel lane (Arc 7) — 2B-1 MERGED; 2B-2 IN FLIGHT
 
 Stage 1, the Stage 2 framing, Stage 2A, and **Stage 2B-1 are all on
 `main`**. Framing revision 5's three-way split of 2B was explicitly
 approved on 2026-07-27; revision 6 records PR #184's review correction.
-Nothing in this arc is in flight. **2B-2 — the daemon panel projection
-and epoch machine — is the next slice, and it branches fresh from
-`githubsucks/main` @ `6bee09d` or newer. Do not stack it on the 2B-1
-branch.**
+**2B-2 — the daemon panel projection and epoch machine — is under way**
+on branch `bottom-panel-stage2b2`, worktree `../pmacs-bp-stage2b2`,
+branched fresh from `githubsucks/main` @ `6bee09d`. It is *not* stacked
+on the 2B-1 branch, which is the rule for every slice in this arc. Note
+that `main` has since advanced to `0442d78`; the only difference is the
+test-only #174, so the slice's integration surface is unchanged.
+
+**2B-2's boundaries, restated because they are easy to overrun:** the
+production `Hello` stays at v20 and `panel_capable` stays `false`. The
+slice is dark/test-only capability exactly as 2B-1 was. Compatible v21
+activation, the GPU band, and the negotiated capability flip are all
+2B-3's, and 2B-3 may **not** simply change the unsolicited `Hello` to
+21.
 
 - **Stage 2B-1 MERGED as #184** (`main` @ `6bee09d`, 2026-07-28; all
   twelve checks green on the reviewed head `5539b6e`; two review rounds
@@ -446,64 +459,6 @@ has **no branch and no framing yet**.
   `FrontendView.fold_projection` to `true` for semantic frontends, which
   Stage 2 deliberately left `false` (Q#FD21).
 
-## M4 config-sink race lane — PR #174 OPEN, REVIVED AND REGATED
-
-> **This ledger had no lane for #174 at all until this snapshot, and
-> that is the defect worth naming.** An open PR is precisely the
-> volatile work this file exists to record; two of them were invisible
-> here (see the dired framing lane below), which is how one of them
-> drifted 153 commits without anyone noticing.
-
-- Portable branch: `githubsucks/fix-m4-sink-races`; worktree
-  `../pmacs-m4-sink-race`. **PR #174**, base `main`.
-- **Revived 2026-07-28**: it was 130 commits behind, so canonical `main`
-  @ `6bee09d` was merged in at `302c21c` and the whole gate suite rerun.
-  The diff against `main` is unchanged at **25 lines in one file**
-  (`tests/m4_acceptance.rs`).
-- **The fix is one predicate.**
-  `m4_5_initial_config_pushed_via_did_change_configuration` waited for
-  `contains("probe")` and then asserted `"probe":true` — six bytes
-  further on. The sink is JSONL written by a *separate process*, so the
-  test could read a half-written line; Linux wins that race reliably and
-  macOS/lua54 did not, reporting `{"rust":{"probe":`. It now waits for a
-  trailing newline, which is true only once a whole record has landed.
-  **Any "wait until the file mentions X, then assert Y about the file"
-  shape races whenever Y is stricter than X.**
-- **The structural claim was re-verified against current `main`, not
-  inherited from the original scout.** `src/bin/pmacs_fake_lsp.rs` *did*
-  change upstream (Lean 4 stages 3b, `1e1be67` / `cdaea66`), so the "one
-  `writeln!` is the only writer" argument could have rotted. It has not:
-  the config sink is still a single `writeln!` at `:433` on a
-  `create+append` handle. `tests/m4_acceptance.rs` itself has **zero**
-  upstream commits since the merge base `ccf29e3`, which is why the
-  merge was clean.
-- **The race cannot be falsified locally, but the wait can be — and was,
-  two ways.** Replacing the predicate with an unsatisfiable one fails
-  the test at `m4_acceptance.rs:317` with "async pump deadline
-  exceeded", proving `pump_async` asserts rather than falling through
-  and that the new predicate genuinely has to become true. Restoring the
-  *old* predicate leaves the test passing locally, which confirms rather
-  than assumes that a green local run cannot tell the two apart. Treat
-  the local suite as a regression check and the structural argument as
-  the reason.
-- **The sibling weak predicate is deliberately left alone.** `m4_26`
-  (`:5487`) has the same shape, and the obvious fix makes it *worse* —
-  waiting for the expected value turns a genuine `rootUri` regression
-  into a five-second timeout with a misleading message, trading a
-  precise diff for a vague hang. Closing it properly means giving that
-  sink a record terminator in the fake server, and it has never been
-  observed failing. The reasoning is a comment at the call site so the
-  next person does not repeat the first instinct.
-- Gates on `302c21c`: fmt; strict workspace Clippy; library **1,849 + 3
-  ignored** default and **2,034 + 4 ignored** CRDT; m4 **121 passed + 3
-  ignored + 1 filtered** with basedpyright skipped; the two touched
-  tests run explicitly **2/2**; required GPU **202/202**;
-  `git diff --check`.
-- **No ledger entry was added on the PR branch itself** — this file was
-  owned by the landed-state sync while #174 was revived, and a
-  drive-by lane there would have re-conflicted it for no benefit. This
-  is that entry.
-
 ## dired Stage 2 framing lane — PR #171 OPEN, STALE, DO NOT MERGE AS-IS
 
 - Portable branch: `githubsucks/dired-stage2-framing` (head `ab42a79`,
@@ -536,7 +491,11 @@ has **no branch and no framing yet**.
     fan-out a rename transaction has to survive.
 
   Re-scout against `6bee09d`, publish a new revision, and get explicit
-  framing approval before any implementation.
+  framing approval before any implementation. **The re-scout is under
+  way** on the existing branch, so PR #171 keeps its three-round
+  history; the product is a revision 5, not a new document. (`main` has
+  since advanced to `0442d78`, but the only difference is the test-only
+  #174, so no re-scout conclusion turns on it.)
 - **The rename problem the framing must still answer**, restated because
   it is the hard part: a rename is a transaction across **five** path
   owners — the buffer path, the buffer name, the URI-keyed LSP stores

docs/agent-handoff.md

@@ -1,7 +1,9 @@
 # Agent handoff — cross-machine continuity
 
-**Last updated: 2026-07-28, after bottom-panel Stage 2B-1 (#184) merged;
-the canonical landed base is that merge — the reserved protocol-v21
+**Last updated: 2026-07-28, after the M4 config-sink race fix (#174) and
+bottom-panel Stage 2B-1 (#184) merged; the canonical landed base is
+`0442d78`. #174 is test-only. #184 is the substantive one — the reserved
+protocol-v21
 bottom-panel wire family, dark by construction, with the production
 handshake deliberately still advertising v20 — following the Journey/GPU
 directory-target ratchet (#183), following Journey Stage 1a (#182),
@@ -49,7 +51,8 @@ commands, read `docs/active-work.md` immediately after this file.
 
 ## 1. Where the project stands (2026-07-28)
 
-- `main` @ `6bee09d` (bottom-panel Stage 2B-1 #184, atop the Journey/GPU
+- `main` @ `0442d78` (the M4 config-sink race fix #174 — test-only —
+  atop bottom-panel Stage 2B-1 #184, the Journey/GPU
   directory-target ratchet #183, Journey Stage 1a #182, incorporating
   terminal configuration + copy
   mode landed docs #180, Lean 4 Stage 4b #181, the dired Stage 1 landed
@@ -528,7 +531,7 @@ commands, read `docs/active-work.md` immediately after this file.
     negotiated `panel_capable` flip. Production attachment remains v20
     through 2B-2. Parent acceptance 37–55 remains authoritative.
     Stage 3 is the adopter default flip. **2B-2 is the next slice, and
-    it branches from `6bee09d` or newer.**
+    it branches from `0442d78` or newer.**
   - **The §1.3 census is CLASSIFIED, not uniformly redirected.** Only the
     Projection class (#1–#12, #21–#22) routes through
     `primary_document_window`; focus/input (#13–#15, #23), focus chrome
@@ -1412,6 +1415,33 @@ round-trip cannot detect a discriminant shift.
   0/15 failures with all 16 cores saturated versus 1/10 for the ticking
   helper.** The general rule: an observation helper that advances the
   system is not an observation.
+- **A wait predicate that is WEAKER than the assertion it guards is a
+  race, on every platform that happens to lose it.** #174: the m4 config
+  sink test waited for `contains("probe")` and then asserted
+  `"probe":true` — six bytes further on. The sink is JSONL written by a
+  *separate process*, so the test could read a half-written line; Linux
+  won that race reliably and macOS/lua54 did not, reporting the
+  truncated `{"rust":{"probe":`. **Any "wait until the file mentions X,
+  then assert Y about the file" shape races whenever Y is stricter than
+  X.** The fix is to wait for the exact unit the assertion reads — here
+  a trailing newline, true only once a whole `writeln!` record has
+  landed, and still correct if the payload's field order or spelling
+  changes. Two things generalize beyond the fix:
+  - **A race you cannot reproduce can still be bitten at one remove.**
+    The failure needs a scheduler outcome Linux does not produce, so no
+    local run falsifies it. But `pump_async` *asserts* on its deadline,
+    so replacing the predicate with an unsatisfiable one proves the wait
+    is load-bearing rather than decorative — and restoring the *old*
+    predicate, which still passes locally, proves a green local run
+    cannot distinguish the two. Bite what you can reach and say plainly
+    which claim rests on structure instead of evidence.
+  - **The obvious fix is sometimes worse.** The sibling `m4_26` has the
+    same weak shape and was deliberately left alone: waiting for the
+    expected value would convert a genuine `rootUri` regression — what
+    its `assert_ne!`s exist to catch — into a five-second timeout with a
+    misleading "server didn't initialize?" message, trading a precise
+    assertion diff for a vague hang. Closing it properly needs a record
+    terminator in the fake server first.
 - **Proving a child has exited is harder than it looks on this
   codebase.** A fixed sleep is not proof; nix's `waitid` is unavailable
   on macOS; and `libc::waitid` needs `unsafe`, which