FN-6198: unquarantine self-healing db corruption test

Restore the self-healing DB corruption test to the default engine suite.

- remove the engine vitest exclude for self-healing-db-corruption.test.ts
- clear the quarantine ledger entry for the restored test

Files changed:
 packages/engine/vitest.config.ts | 1 -
 scripts/lib/test-quarantine.json | 8 +-------
 2 files changed, 1 insertion(+), 8 deletions(-)

Fusion-Task-Id: FN-6198

Fusion-Task-Lineage: 2466b040-956d-4138-89d5-137d1721081c

scripts/lib/test-quarantine.json

@@ -1,10 +1,4 @@
 {
   "$comment": "Flaky-test quarantine ledger (deletion ratchet — see AGENTS.md 'Flaky tests: quarantine on sight' and docs/testing.md 'Quarantine ledger and the deletion ratchet'). A test observed failing without a corresponding real bug is quarantined ON SIGHT: add an entry here AND a matching one-line `exclude` entry in that package's vitest config, in the same commit. Every entry needs a non-empty `reason` (link the failing run) and a `quarantinedAt` date — the entry expires 14 days later, at which point the test file is DELETED unless someone rescues it with evidence it catches real regressions plus a root-cause fix (never appeasement). There is deliberately no loader module and no automation around this file: it is a dated record, the vitest config exclude is the mechanism, and the sweep is policy executed by whoever touches the suite.",
-  "entries": [
-    {
-      "file": "packages/engine/src/__tests__/self-healing-db-corruption.test.ts",
-      "reason": "FN-6195: observed flake when runMaintenance() scanned the real OS tmpdir and picked up stale fusion-ai-merge-* worktrees from unrelated tests, adding unexpected audit calls. Failing run: Fusion task FN-6195 agent verification log, 2026-06-10.",
-      "quarantinedAt": "2026-06-10"
-    }
-  ]
+  "entries": []
 }