Advance Blender 5.2 web parity through M12-03D

docs/status/M12-01G.md

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+# M12-01G Status
+
+status: done
+task: preserve the old catalog index when an IndexedDB migration fails
+updated: 2026-08-17 America/New_York
+enablingTask: true
+parityStateChange: false
+
+## Scope
+
+The production IndexedDB migration prepares schema v2 with the existing schema v1 parser and
+migrator before opening a write transaction. It then rechecks the source row and atomically
+writes the v2 index and migration receipt while deleting the v1 row. A concurrent source change
+returns `REVISION_CONFLICT`; a transaction failure returns `STORAGE_TRANSACTION`.
+
+The browser suite injects failures after the v2 target write and after the v1 source delete.
+After each abort it closes and reopens the database, proving the database version, complete v1
+index, unrelated legacy migration row, absent v2 row, and absent receipt are byte-for-byte
+equivalent to the baseline. A subsequent retry commits the v2 index and receipt together.
+
+## Evidence
+
+- `WEB_TEST_PORT=5593 npm --prefix web run test:asset-catalog-indexeddb-migration` passed the
+  M12-01D production migration unit suite 3/3, the M12-01G artifact binding unit 1/1, and
+  Chromium 1/1.
+- Both `AFTER_TARGET_PUT` and `AFTER_SOURCE_DELETE` returned `STORAGE_TRANSACTION`; reopening
+  IndexedDB after either fault produced the exact pre-migration snapshot.
+- The successful retry preserved revision 7 and the M12-01D source/target hashes, removed only
+  the v1 row, and retained the unrelated migration row.
+- Typecheck and `git diff --check` passed.
+
+## Artifact Hashes
+
+- production IndexedDB migration: `283a08bccb5ea301bd2aef8f01d4496972e3962f75e340479336c50e3539ba57`
+- browser suite: `82c40f38898277b4053a9654537ec9c21bc01a784d1091831e139361575a81e9`
+- artifact unit: `a4366a16f28b91b3ff213e0232308eaecd392731f27972cfa49a11568eb0feca`
+- manifest: `2596067956211698f1b7a07d9423411e2db830b72e6b78593354953a568738e7`
+
+## Next Task
+
+`M12-01H`: prove catalog ordering and asset identity survive page and Worker restarts.
+
+## Rollback
+
+Remove the IndexedDB migration module, M12-01G unit/browser suites, manifest, package command,
+and this status entry. Restore M12-01G to pending and `nextTask` to M12-01G. No parity ledger
+rollback is required.