feat(planning): detect an interview page server older than the page it serves #9718

Parent

Refs #5796

Depends on

• none: on the frontier now

Outcome

A page server started before a plugin update is detected and restarted instead of silently running old logic
(gap G10; not done on main: no /api/state field reports the server's plugin version).

• /api/state reports the server's plugin version and a hash of its own source, taken at start.
• The page compares them with its embedded version and shows "This page's server is older than the page. Run
  ensure-running to restart."
• round.sh ensure-running restarts a running server whose recorded version differs from the installed one.
• watch.sh prints a note: line when it sees the mismatch.

Key interfaces

• Interview page: plugins/planning/surface/index.html; page server: plugins/planning/surface/server.py
  (record(), derive_states); round CLI: plugins/planning/surface/round.py behind round.sh;
  exporters: plugins/planning/surface/exporters.py.
• The interview skill's surface contract, plugins/planning/skills/interview/context/surface.md, documents
  every new op, field, setting and refusal.
• plugins/planning/surface/watch.sh.

Done when

• A server test reads /api/state and finds the plugin version and source hash fields.
• A test starts a server with a recorded version different from the manifest's, runs ensure-running, and finds a new server PID serving the manifest version.
• A page test with a mismatched version shows the banner.
• bash plugins/planning/surface/watch.test.sh exits 0 with a case asserting the note: line.
• scripts/run-test-file.sh plugins/planning/surface/test_server.py exits 0.
• scripts/run-test-file.sh plugins/planning/surface/test_round.py exits 0.
• bash plugins/planning/surface/surface.test.sh exits 0, so a data dir without the new fields still loads, renders and exports.
• scripts/check-changelog-fragments.sh --check-required origin/main exits 0.