Checkpoint web parity through Chromium input tasks

docs/status/M12-04H.md

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+# M12-04H Status
+
+status: done
+task: remove extraction staging on cancellation without modifying the committed project
+updated: 2026-08-18 America/New_York
+enablingTask: false
+parityStateChange: false
+
+## Scope
+
+The production archive extraction transaction checks cancellation before staging, around every
+payload read and write, and immediately before atomic commit. A pre-commit cancellation returns
+`IO_ARCHIVE_CANCELLED`, removes every staged file, publishes no project, and re-reads the committed
+project identity to prove that revision and SHA-256 did not change. Once atomic commit starts,
+cancellation no longer converts the completed commit into a cancelled result.
+
+Payload identity failure and staging creation/write failure use the same cleanup path. If cleanup
+leaves a staged entry or the committed identity drifts, the transaction fails with
+`STORAGE_TRANSACTION` instead of claiming successful cancellation.
+
+## Evidence
+
+- `npm --prefix web run test:library-archive-cancellation` passed 6/6 unit tests against real
+  temporary directories.
+- Cancellation before staging, after one staged file, and after the final staged write all leave
+  zero staging files, zero published projects, and the original committed project bytes.
+- The success path publishes revision 9 only after both staged payload hashes pass.
+- Payload mismatch, rollback identity drift, stale revision, unsafe path, prefix conflict, and
+  undeclared-field negatives fail closed.
+
+## Artifact Hashes
+
+- parent manifest: `c35e675e8f512e85b748f0b5578874fed8c99df7674a152e698236a67c9f4fa4`
+- protocol: `c40adc1449172014cc1820db567e155828314abb404b66e4de13c26ddee06e4b`
+- error codes: `751c70c898540fa7e82fb1b1a79254756ec8db8e4201a88b6d817d7c3d92103f`
+- unit: `77e7d5bc64dd6b313006ebf523602601acdaf7949a1484da872ddcd046983786`
+- package commands: `cfb232baa494ff59f6c8d65514a08c86332ee9354350b2a0392b6f932a7ee42c`
+- manifest: `7fce600a416aec5ade1a91a13d86caf4cb1f65b710054b59d525ff8b1d3c7409`
+
+## Next Task
+
+`M12-04I`: release temporary files after quota/OOM and allow a small archive to recover.
+
+## Rollback
+
+Remove the extraction transaction protocol, cancellation code, real-filesystem unit suite, manifest,
+package command, and this status entry. Restore M12-04G as the queue tail and move the machine queue
+back to `M12-04H`. No parity ledger rollback is required.