* test(#4091): RED — worker cache write must be rename-atomic
Structural regression guard: gsd-check-update-worker.js must not write the
shared per-package cache in place; assert temp+rename publish shape plus a
behavioral no-residue e2e.
* fix(#4091): publish update-check cache via atomic temp+rename
writeFileSync on the shared per-package cache truncates before writing, so
concurrent cross-runtime readers (statusline/banner) could see a torn or
empty record. Stage under a unique same-directory temp and rename into
place — POSIX rename(2) is atomic, so readers see the old or new record,
never a partial one. Degrade policy (#3582) unchanged: errors swallowed,
temp best-effort removed.
* refactor(#4091): hoist temp path, tighten uniqueness assertion (review)
* changeset(#4091): add fragment (pr backfill to follow)
* changeset(#4091): backfill PR 4313
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Co-authored-by: sim <sim@local>
d9d16551b7