Checkpoint web parity through Chromium input tasks

docs/status/M13-04J.md

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+# M13-04J Status
+
+status: done  
+task: server request idempotency and conflict isolation  
+updated: 2026-08-19 America/New_York  
+enablingTask: false  
+parityStateChange: false
+
+## Scope
+
+`projectId/requestId` is now an idempotency key. An exact retry verifies and reuses the existing result;
+different output or source/settings/build identity returns a stable conflict and cannot overwrite the bound
+result. Different requests use separate result and receipt files. Concurrent duplicate requests share one
+in-flight submission and resolve as one commit plus one reuse. Execution remains `DISABLED`.
+
+## Evidence
+
+- `npm --prefix web run test:server-job-idempotency` passed 3/3 unit tests and the checker.
+- Checker output: `server-job-idempotency-ok first=COMMITTED retry=REUSED conflict=BLOCKED isolated=1 concurrent=REUSED execution=DISABLED next=M13-05A`.
+- `git diff --check` passed.
+
+## Artifact Hashes
+
+- parent manifest: `f9658954d3dbd0cd1edd696c10f6a1b880bb3288c91a39a47ca84c4496046a97`
+- protocol: `15eca7550964c9985e26a22a7900d3f3aa69fdef35fe5962b48a8f55ebba5863`
+- checker: `02247ffda07c095373642a7fa22268bb9f5ac181d41571f7fff685812976d3c4`
+- unit: `6ee08e67cd8493e856f67309bd6562316eca42ef52dd4a9aad3a15efdc4b6b41`
+- package: `5b47e94cf828fc9d3021019eed9922eb67815aba5416266d8c967c7cb5bd96ba`
+- report: `31f95a8cc1c4792303986b8b5987ab02fc11a77ab25fd76b31c02d1ed1b104d1`
+
+## Next Task
+
+`M13-05A`: CSP denies inline script, eval, data script and undeclared origins.
+
+## Rollback
+
+Remove the idempotency protocol, unit/checker, report, manifest, package command and this status entry;
+restore `M13-04I` as the queue tail.