Advance Blender 5.2 web parity through M12-03D

docs/status/M12-02E.md

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+# M12-02E Status
+
+status: done
+task: deduplicate identical preview content without merging asset metadata
+updated: 2026-08-17 America/New_York
+enablingTask: true
+parityStateChange: false
+
+## Scope
+
+Two catalog assets with distinct Blender weak-reference identities and distinct catalog metadata
+may bind the same verified preview content. The M12-02D coordinator keys OPFS storage only by the
+content SHA-256, while catalog entries and preview identity hashes remain asset-specific. A second
+commit of identical bytes reuses the existing payload after a full readback/hash check.
+
+No catalog metadata is derived from or stored inside the shared payload record. Each transaction
+updates only its targeted asset's preview field and advances the guarded catalog revision.
+
+## Evidence
+
+- `WEB_TEST_PORT=5597 npm --prefix web run test:asset-preview-dedup` passed the artifact unit test
+  1/1 and real Chromium OPFS/IndexedDB test 1/1.
+- Two distinct asset/identity hashes committed at revisions 8 and 9; the second commit reported
+  `deduplicated=true` and the OPFS content directory contained exactly one final file.
+- Both catalog entries referenced the same 513-byte/hash payload while their complete non-preview
+  metadata remained byte-for-byte equal to their different baseline records.
+- Database reopen reproduced revision 9, the second asset head receipt, and the shared preview;
+  stored payload bytes rehashed to the declared content digest.
+
+## Artifact Hashes
+
+- Chromium suite: `4e53b7a35eb109b152bd6dc0c3348dcb08879d17619968d37fc761c67aa38b40`
+- unit suite: `e023fdd33e0f40c1331dfdd73cd287dc684256b9d134971ab17db8cfe2a83835`
+- manifest: `7d25f1d8335481795257c643c8589d1607a865634b27a7e5d145a57ce2a92a62`
+- package commands: `5a83676e821bb768f6d3e282ea4728413cf84c5f3d57672fc664fac3883873e5`
+
+## Next Task
+
+`M12-02F`: quarantine corrupt preview content while keeping asset metadata readable.
+
+## Rollback
+
+Remove the deduplication Chromium/unit suites, M12-02E manifest, package command, and this status
+entry. Restore M12-02E to pending and `nextTask` to M12-02E. The shared coordinator and parity
+ledger do not require rollback.