The framing and the lane are this branch's FIRST commit, which is the
arc's §5 rule for every PR in it and the reason this branch exists
before any code: revision 9 was approved as an untracked file, and an
approved framing that lives in one worktree is not portable.
Revision 9 landed after EIGHT rejected revisions. The through-line of
those rounds is worth carrying: each early draft turned a fresh source
audit into SCOPE LABELS --- "DroppedFile", "translate_key completion",
"no behaviour change" --- and review kept asking the same question,
which is what the label means when someone has to test it. Revision 9 is
a contract/witness/mutation matrix over every numbered clause, split
into CHANGE clauses that fail today and PRESERVATION clauses that pass
and must keep passing.
Several findings only existed because the contracts were written down.
"Send Detach before exit" was unexecutable against an outbox whose
`enqueue` rejects once closed. A one-slot terminal reservation
contradicted the FocusLost-before-Detach ordering two sections above it.
"Terminal result after the commit resolves" was not total over a
pipeline with three legitimate exits that never commit --- a claimed
listener, a cleared handler slot, and the default handler's `open_async`
returning immediately. None of those are visible from a scope label.
This branch is 1-pre ALONE: the input seam, no behaviour change. Its
evidence is a headless routing harness recording routing decisions,
outbound events AND local effects, with production `window_event` as a
thin call-through. P3 is recorded as an accepted structural exception:
a headless test cannot construct `ActiveEventLoop`, so the delegation
itself is a code-review invariant rather than a tested one, and saying
so is better than a mutation that cannot exist.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016bqGA6s9tTUFzYpbeW3tai
