feat(planning): gate interview page answers on open prerequisites and expect declared dependencies #9709

Parent

Refs #5796

Depends on

• none: on the frontier now

Outcome

Saving a decision on a question whose dependsOn names a still-open question follows a frontierLock
setting, and skills are expected to declare dependsOn so the lock has data to act on.

• frontierLock: confirm (default): Save on a blocked question opens "Q100 depends on Q22, which is still
  open. [Go to Q22] [Answer anyway]". Answer anyway sends outOfOrder: ["Q22"], which the server stores; when
  Q22 is decided, derive_states marks Q100 stale. The rail shows a padlock chip in place of Blocked.
• frontierLock: hard: the server answers 409 {"error": "blocked", "waitsOn": [...]}.
• frontierLock: off: today's behavior.
• Ask, Rephrase and Research this stay enabled in every mode.
• add and add-round warn when a question omits dependsOn ([] declares independence) and when it names
  a question open in the same round; under a requireDepends setting both refuse. surface.md "A round" states
  the rule beside commits, and the interview skill requires every posted question to declare dependsOn.

Decisions

• G1 (owner, 2026-10-18, batch item D5): default confirm, shipped together with G2, because 0 of 87
  questions declared dependsOn, so a lock alone does nothing.
• Constraint C8: ship defaults, every behavior tunable.
• feat(planning): redesign the interview page for the multi-round flow #4547 Answer-anyway contract: confirm keeps answering one click away.

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.

Done when

• A server test sets frontierLock: hard, saves on a blocked question and gets 409 with "error": "blocked" and the open ids in waitsOn.
• A server test under confirm stores outOfOrder on the event, and a later decision on the prerequisite derives stale for the dependent.
• Round tests: add without dependsOn exits 0 with a warning naming the id; add naming a same-round open question warns; both exit non-zero under requireDepends.
• A page test shows the confirm dialog with "Go to" and "Answer anyway" on a blocked save, and Ask enabled under hard.
• grep -n "frontierLock" plugins/planning/skills/interview/context/surface.md and grep -n "requireDepends" plugins/planning/skills/interview/context/surface.md each print a 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.

Out of scope

• Marking dependents when an earlier answer changes (its own slice under feat(planning): interview page does not enforce answer order or react to changed answers like the terminal interview #5796).
• Constraint staleness (planning: mark interview recommendations stale when a new constraint arrives mid-interview #5769).