Visual browser smoke: walk through examples/chat CHECKLIST.md in real Chrome

[blove]

Context: PR #213 landed the canonical examples/chat demo + smoke generator (Phase 1). All 14 CI checks green. Server-side regenerate-path probe via curl confirmed the demo's wire-shape works against the new graph (state correctly transitions 1u/1a → 1u/0u via as_node='__start__' rollback → 1u/1a with new AI id, the 0.0.29 fix path).

What's still pending: Visual browser sweep through examples/chat/smoke/CHECKLIST.md against the generated ~/tmp/ngaf consumer. The Chrome extension MCP was offline at merge time; only server-side and unit-test validation completed.

Steps to close this issue

1. Pull latest main: git pull origin main.
2. Confirm OPENAI_API_KEY in examples/chat/python/.env.
3. Generate fresh smoke consumer:

   npx nx run examples-chat-smoke:run
   # Accept default: ~/tmp/ngaf, version=latest, install=Y, start=N

4. Start backend: cd examples/chat/python && uv run langgraph dev --port 2024 --no-browser
5. Start the smoke consumer: cd ~/tmp/ngaf && npm start
6. Open http://localhost:4200 in Chrome.
7. Walk through every section of ~/tmp/ngaf/CHECKLIST.md:
   • Pre-flight, initial render, send & receive, stop mid-stream
   • Markdown surfaces (headings, bullets/ordered, task lists, fenced code, tables, blockquotes, links, HRs, no raw HTML escape) — single most important section since it exercises the partial-markdown render path
   • Streaming-specific markdown checks (incomplete code block / table mid-stream)
   • Regenerate with the 1u/1a server-state assertion via curl /threads/<id>/state
   • Cross-mode persistence
   • Mode switching (route + URL, deep-link, popup/sidebar role checks)
   • Model picker (note: known issue — initial dropdown shows first option gpt-5 instead of the signal value gpt-5-mini; capture as a follow-up if confirmed)
   • Debug overlay mount/unmount
   • Palette UX (collapse/expand persistence)
   • Keyboard & accessibility
   • Error handling (stop python; resume)
   • Lifecycle (reload mid-conversation, "↻ New conversation" reset)
   • Browser hygiene (no console.error, no detached chat-message nodes after 10 mode-switch cycles)
   • Visual polish at 1440 / 1024 / 768 / 480
8. Capture ~/tmp/ngaf/SMOKE_RUN.md plus any screenshots / HAR exports for failures.
9. File targeted issues against libs/chat for any regressions (e.g. tables / task-lists are documented known regressions from the 0.0.20 partial-markdown swap — surface them here too if still present).

Done when

• All Phase 1 sections of CHECKLIST.md walked.
• SMOKE_RUN.md captured (or note "all green, no capture needed").
• Any failures filed as separate issues against libs/chat.