New builtin/runtime/comment.lua: `edit.toggle-comment` comments or
uncomments the current line — or every line the region touches — using
the language's line prefix from the public, user-extensible
`pmacs.comment.strings` table (Q#CT3; block comments deferred).
Language detection reuses lsp.lua's grammar+filetypes chain, now
exported as `pmacs.lsp.active_buffer_language()` (the only lsp.lua
touch — one assignment).
Semantics (Q#CT4): uncomment iff every non-blank line already starts
(after its indentation) with the prefix, stripping the prefix plus one
padding space; otherwise comment, inserting `prefix .. " "` at the
minimum indentation of the span's non-blank lines (Emacs comment-region
alignment). Blank lines are skipped in both directions and don't feed
the min-indent; an all-blank span is a status no-op. Mixed spans
comment — the double prefix round-trips, preserving inner
commented-out code.
The whole toggle is ONE buf:replace (Q#CT5): one undo step (no undo
grouping exists — N per-line edits would need N undos), one CRDT op,
and one effective-edit verification with the killring intercept
discipline (pcall'd; a rejection reports rather than throws; any
post-intercept deviation reports and skips the cursor fix-up).
No-region M-; is Emacs `comment-line`, not `comment-dwim`: toggle,
then move to the next line so repeated M-; walks a block (named
deviation; DWIM's append-at-EOL can come later under its own name).
Region toggles clear the selection and land at the span start. The
command boundary substrate provides chain-break and after-edit for
free (Q#CT6) — asserted anyway.
Tests (comment_toggle_acceptance, 14): rust/lua/python prefixes and
exact round-trips; cursor-next-line incl. the no-trailing-newline
clamp; region min-indent alignment + blank-line skip + selection
clear; mixed-span round-trip; region ending at column 0 excludes that
line; unknown-language and pathless-scratch no-ops; ONE undo restores
a multi-line toggle; rejecting/transforming intercepts (cursor fix-up
skipped); after-edit exactly once on both keybound and M-x paths;
C-k, M-;, C-k breaks the kill chain. Fixture editors empty
pmacs.lsp.config so .rs/.py files never spawn real servers.
Gates: fmt; workspace clippy -D warnings; lib 1500; crdt 1672;
comment 14; killring 30; cua 5; completion 9; autosave 29; m4 100
(--skip basedpyright); GPU 58 (PMACS_REQUIRE_GPU=1); full workspace
sweep clean; git diff --check clean.
Framing: docs/comment-toggle-framing.md.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MtRqijWecEzTjPt1B4Nrt5
