Checkpoint web parity through Chromium input tasks

docs/status/M12-03J.md

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+# M12-03J Status
+
+status: done
+task: desktop override fixture records reference, local owner, and property override path
+updated: 2026-08-17 America/New_York
+enablingTask: false
+parityStateChange: false
+
+## Scope
+
+Blender 5.2 creates a real linked Object and converts it through the library override API. The fixture
+records the linked reference as `SOURCE_LIBRARY/readOnly=true`, the local hierarchy root as
+`LOCAL_OVERRIDE/readOnly=false`, and one explicit custom-property override path. The source marker,
+reference ID, local owner, hierarchy root, property operation and value remain stable after save/reopen.
+
+This fixture does not open a general override writer; it freezes the reference/owner/property contract
+needed by the next bounded writer task.
+
+## Evidence
+
+- `npm --prefix web run test:library-override-desktop` passed.
+- Blender 5.2 source/target fixture regeneration matched the normalized desktop report.
+- The reference retains `m12_override_source.blend`; the local object is `LOCAL_OVERRIDE`; the only
+  recorded property path is `["m12_override_value"]` with value `2.5` and one `REPLACE` operation.
+- Save/reopen preserves the reference, hierarchy root, owner semantics, and property metadata.
+
+## Artifact Hashes
+
+- generator: `2cdbac04cac7240360a9d70919380fd90f9479e2cb41d8032fb51626ed4b4dd6`
+- checker: `afebb3c9b8715b9d2e0c9b17f463f038bd23e8747074137bccbf1c09c4bfb5ba`
+- source blend: `d7f8d78e7e91481bf46ecc9a6bcb01e900a6a397839dd31ab80a53def7675601`
+- target blend: `b008a1608ff1e8f679e1e1281bf7be0360f1137e815dd890cbd93e1e98675495`
+- report: `19cb13a3417b4b65a8497b622337c42c4697b3f3d48de26a1f70f2d4527ddde0`
+- manifest: `01d0f66bb3819eea3e92727d1b5bffbec935d24eeecc28d874b999df78d73fbf`
+- package commands: `cfb232baa494ff59f6c8d65514a08c86332ee9354350b2a0392b6f932a7ee42c`
+
+## Next Task
+
+`M12-03K`: expose exactly one verified override writer property.
+
+## Rollback
+
+Remove the override generator/checker, fixture, report, manifest, package command, and this status
+entry. Restore M12-03I to pending and move the machine queue back to `M12-03J`. No parity ledger
+rollback is required.