Fix comments and a guide path left stale by the delayed-kill, Run end, and installer work

[dormouse-bot]

These are comment and doc fixes only, with no behavior change. Each of these places was left describing code that recent merges changed:

• TESTING_AND_MODIFICATION_GUIDE.md pointed at scripts/window-listeners.test.mjs. That file lives at standalone/scripts/window-listeners.test.mjs, which standalone's test script runs; there is no copy at the repo root.
• requestKill in lib/src/components/Wall.tsx: the docstring still said "a Door reattaches first, an untouched shell closes at once". Since the reopen and delayed-kill work (Reopen closed Surfaces, Workspaces, and windows (⌘⇧T / u / dor reopen) #967, Labs: no-confirm delayed kill (pending kills with a restore window) #969), a close that closeKindOf says won't confirm runs at once, including a Door's close in place. A close that would confirm goes pending under Labs, and otherwise stages the overlay; only that last case reattaches a Door.
• callerTypedTool in lib/src/components/wall/tool-takeover.ts said "both placements need it". A Tool ends with its run; host replacements hold it (scope tool-run, part 1) #979 removed the rerun-in-caller placement, so take-over is now its only consumer.
• The header and extractFunction comments in scripts/installer-verify-test.mjs said each helper is defined once and listed five of them. The script extracts eight helpers, and env_file_value is defined twice in both installers. The script relies on that: it checks that the two copies are identical. The comments now give the actual placement.

node scripts/spec-lint.mjs and node scripts/installer-verify-test.mjs both pass locally.

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[dormouse-bot]

The colon after "checked identical" in the installer-verify-test.mjs header makes the placement list that follows read as the helpers being checked identical, when only env_file_value is. A sentence break fixes it; I'll push the same edit.