Merged after a maintainer rework that kept every one of @HouMinXi's commits intact.
**What the rework added on top of the contribution:** the new DB health-check behaviour is gated behind a default-off feature flag (`src/shared/constants/featureFlagDefinitions.ts`, `defaultValue: "false"`), documented in `docs/reference/FEATURE_FLAGS.md` with the description key carried into all 66 locales, so the release default is unchanged and the new bounds only apply when an operator opts in. The optional-FTS5 migration set was reconciled by hand with the "180" entry that landed meanwhile (`src/lib/db/migrationRunner/constants.ts`).
**Carried from your rebased head:** the `/api/db/health` local-only classification in `src/server/authz/routeGuard.ts` plus its `routeGuard` assertion — `runManagedDbHealthCheck()` forks native diagnostics into a child process, so Hard Rules #15/#17 apply. Re-verified here: 37 pass / 0 fail.
Validated as a combined board first (this PR merged with the 21 siblings of the same wave on the release tip): eslint with the frozen suppressions, typecheck:core, check:open-sse-typecheck, complexity, cognitive-complexity, changelog-integrity, i18n new-key coverage, docs-counts, docs-sync, migration-numbering, provider-consistency and a duplicate-identifier audit all green, plus 176 passing / 0 failing focused node:test cases across the 25 test files the wave touches and the dashboard test under Vitest (2/0). Then re-validated alone on the fresh tip before this merge: conflicts re-resolved, file sizes rebaselined for this PR's own growth, eslint and this PR's focused tests re-run.
Thank you for the depth of this one — the resource-bounds suite and the sql.js startup/backup coverage are the kind of tests that keep a database layer honest.
Closes a real process-killer: the direct-response start timeout could fire after the fetch promise had already settled, and aborting at that point delivered the abort reason to a promise nobody was awaiting — Node promotes that to an `unhandledRejection` → `uncaughtException` and the process dies (#12861). The timer is now a no-op once the attempt has settled, and the same guard is extended to combo hedge cancels and upstream fetch failures.
Validated as a combined board first (this PR merged with the 11 siblings of the same batch on the release tip): eslint on every changed file with the suppressions file, typecheck:core, check:open-sse-typecheck, complexity, cognitive-complexity, changelog-integrity, i18n new-key coverage, docs-sync, migration-numbering, provider-consistency and a duplicate-identifier audit all green, plus 275 passing / 0 failing focused node:test cases across the 28 test files the batch touches. Then re-validated alone on the fresh tip before this merge: conflicts re-resolved, file sizes rebaselined for this PR's own growth, eslint and this PR's focused tests re-run.
Thanks @HouMinXi!
Merged via /merge-batch (lote 2026-08-26, v3.8.51). Boarded no worktree combinado junto com outras ~30 PRs; validação única: typecheck/complexity/cognitive-complexity/changelog-integrity verdes, file-size rebaseado onde necessário (crescimento legítimo), lint com os mesmos 228 achados pré-existentes confirmados via sonda contra o tip puro (não introduzidos por este lote), e ~370 testes focados (unit + vitest) passando. Obrigado pela contribuição.
