fix(#934): reapply verifier handles missing pristine baseline post-rename (#937)

* fix(#934): reapply verifier handles missing pristine baseline post-rename

Gap 1 (verify-reapply-patches.cjs): when backup-meta.json records a
pristine_hash for a file but gsd-pristine/ has no corresponding snapshot
on disk, the verifier fell to over-broad mode and produced false
FAIL_USER_LINES_MISSING. Fix: return advisory OK_NO_BASELINE (non-blocking,
exit 0) so the verifier does not block on files it cannot reason about.

Gap 2 (new migration 004): migration 003 removed legacy get-shit-done/
runtime files but left gsd-pristine/get-shit-done/ orphan snapshots in
place. Those stale snapshots referenced get-shit-done/... key paths that
no longer match the active gsd-core/... layout. Fix: add migration
004-prune-stale-pristine-get-shit-done (NOT editing 003, preserving its
checksum — ref #670 guard) to remove all files under
gsd-pristine/get-shit-done/ as GSD-managed pristine snapshots.

Includes tests: bug-934 OK_NO_BASELINE assertions in the verifier test,
new installer-migration-prune-stale-pristine.test.cjs, updated
installer-migrations baseline-lock checksum for 004.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* fix(#934): rename migration to satisfy legacy-name guard + mark intentional path refs

Rename src/installer-migrations/004-prune-stale-pristine-get-shit-done.cts
→ 004-prune-stale-pristine-snapshots.cts so the filename no longer contains the
forbidden token.  Update .gitignore and eslint.config.mjs to track the new built
path.  Add gsd-allow-legacy-name markers to the remaining intentional uses of the
legacy path string in the migration body (lines 3 and 100) and in tests
(installer-migration-prune-stale-pristine.test.cjs lines 202 and 226; and the
baseline-lock key in installer-migrations.test.cjs:1469).  Update the baseline
checksum for migration 2026-06-09-prune-stale-pristine-get-shit-done to reflect
the two new marker comments added to its body.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

---------

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

eslint.config.mjs

@@ -78,6 +78,7 @@ export default tseslint.config(
       'gsd-core/bin/lib/federated-config.cjs',
       'gsd-core/bin/lib/installer-migrations/002-codex-legacy-hooks-json.cjs',
       'gsd-core/bin/lib/installer-migrations/003-rename-get-shit-done-to-gsd-core.cjs',
+      'gsd-core/bin/lib/installer-migrations/004-prune-stale-pristine-snapshots.cjs',
       'gsd-core/bin/lib/observability/logger.cjs',
       'gsd-core/bin/lib/active-workstream-store.cjs',
       'gsd-core/bin/lib/adr-parser.cjs',