Checkpoint web parity through Chromium input tasks

docs/status/M12-03I.md

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+# M12-03I Status
+
+status: done
+task: missing library preserves placeholder and original source reference
+updated: 2026-08-17 America/New_York
+enablingTask: false
+parityStateChange: false
+
+## Scope
+
+Schema-1 missing-library requests match a linked source library by source identity, generation, and
+revision. Marking a matching reference missing changes only its status and adds a
+`MISSING_LIBRARY` placeholder. The original locator, source SHA-256, generation, revision, and every
+data-block ID remain attached to the reference; unrelated libraries remain unchanged.
+
+Stale generation/revision and source hash drift return a stable conflict without deleting or replacing
+the reference. Malformed fields, duplicate identities, and inconsistent placeholder data fail closed.
+
+## Evidence
+
+- `npm --prefix web run test:library-linked-missing` passed 4/4 unit tests.
+- The matching case preserves original source metadata and data-block IDs while publishing only the
+  placeholder status transition.
+- Stale, source-drift, undeclared-field, duplicate-identity, and invalid-placeholder cases publish no
+  partial state.
+
+## Artifact Hashes
+
+- protocol: `5833e8c943ef6bd866a93a0e1666c9521fa6d3e8358861df57b628874b679ec2`
+- unit: `4ab6d6ff4845b4ca963399e7eea214ceb412871dc1fdef5bac1ed0333596da4f`
+- manifest: `f5fa606161b93e9ee42e7ca8144d2a83379acf601c5045eb8cc76732f8dba431`
+- package commands: `cfb232baa494ff59f6c8d65514a08c86332ee9354350b2a0392b6f932a7ee42c`
+
+## Next Task
+
+`M12-03J`: desktop override fixture records reference, local owner, and property override path.
+
+## Rollback
+
+Remove the missing-library protocol, unit suite, manifest, package command, and this status entry.
+Restore M12-03H to pending and move the machine queue back to `M12-03I`. No parity ledger rollback
+is required.