feat(engine): entry-gate + phase-note — entry validation derives engine-side

[leeovery]

Stage 6b of the render-surfaces programme (design log: #489; base: #496). The last surface family: entry prerequisite validation moves from prose read-and-branch to engine derivation.

Surfaces

render entry-gate <wu>.<phase>.<topic> — full absorption: the engine reads the manifest and returns either an empty response (clear — the flow proceeds) or the terminal DISPLAY: entry blocker. State machines per target phase:

• planning — every specification status mapped: missing, in-progress, proposed ("Not Started"), superseded (naming the superseding topic), promoted (naming the cc unit); completed = clear.
• implementation — plan missing / not completed.
• review — plan missing / implementation missing / implementation not complete.
• specification — work-type-aware: feature & cross-cutting check the topic's discussion; bugfix the investigation; epic requires at least one completed discussion (with the distinct no-discussions vs none-completed blocks).

validate-spec.md (6 conditional blocks + a manifest read) and validate-source.md (4 work-type branches × 2-3 blocks + reads) each collapse to one call and two branches; implementation/review validate-phase drop their read-and-branch prerequisite sections. Every blocker text byte-matches the old prose.

render phase-note <wu>.<phase>.<topic> --verb <Word> [--noun <word>] — the entry one-liners (Resuming/Reopening/Starting …), ten templates swapped across seven entries (planning keeps its "Reopening plan" wording via --noun).

Selection not-found — the continue-* view snapshot for an unknown name now appends the per-type terminal display; five validate-selection references emit the section instead of authoring it.

Test plan

• entry-gate: the full state matrix — 6 planning states, 3 implementation, 4 review, and the work-type-aware specification set including both epic variants; unsupported phase is loud.
• phase-note default/override/validation; not-found byte-exact per type.
• npm test — 1518/1518. Typecheck + conventions lint clean.

🤖 Generated with Claude Code

Stack

1. feat(engine): render surface catalogue — resume-gate and task-list pilots #490
2. feat(engine): finding + findings-summary surfaces — review-findings loop unified #491
3. feat(engine): task-gate surfaces — proposed-task, tasks-overview, author-task-gate, phase-tree #492
4. feat(engine): selection projection + bridge continuation surfaces #493
5. feat(engine): transaction confirmation sections — lifecycle verbs carry their own chrome #496
6. feat(engine): entry-gate + phase-note — entry validation derives engine-side #497 👈 current
7. feat(engine): the fence is the frame — boxedFrame retired (D8) #498
8. feat(engine): topic complete + discovery-session close fold their kb warnings (7a) #499
9. feat(engine): resume-gate variants + entry-gate --own + phase-completed --paths (7b) #500
10. test(conventions): templated-fence ratchet — check 13 lands D4 (7c) #501