fix(docs): keep quickstart demo restarts and approvals consistent

[Birfy]

Changes

• Cancel stale asynchronous demo continuations when a new conversation starts, including restarts during run and apply playback.
• Snapshot the planned artifact so preset edits cannot change the approved diff.
• Add 10 deterministic JavaScript DOM/timer interaction tests and run them in docs CI.

Addresses #208 (comment) and #208 (comment).

Current integration

Forward-merged main edcd65c into head bd69a74. The refreshed website's theme, install, artifact-picker and recipe interactions are preserved. Only the original three scoped fix/test/CI files differ from that main. #211 independently resolved both earlier baseline documentation failures, so this PR no longer depends on #207.

Verification

• Node deterministic DOM/timer suite: 10 passed on the integrated code; 6 tests fail on the unfixed implementation.
• Focused Python documentation checks: 10 passed, including the formerly failing anchor/port-count checks.
• node --check docs/assets/experience.js and git diff --check passed.
• Refreshed independent review found no blocking findings; 19 additional in-memory boundary/path scenarios passed and contributor theme/install/recipe/artifact interactions were verified unchanged from main.
• Deterministic DOM harness only; no rendered browser validation is claimed.
• Exact-head bd69a74 CI passed all four Python 3.9/3.10/3.11/3.12 suites, wheel builds and smoke gates, plus strict MkDocs and Node regressions. Evidence: docs, Python matrix and wheel gates. Prior-head results are not this head's evidence.

Marked ready for review after independent review and exact-head CI passed. This task did not merge, release, or deploy.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-10T07:29:13.883782Z	bd69a74	Draft marked ready

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