feat(engine): task-gate surfaces — proposed-task, tasks-overview, author-task-gate, phase-tree

[leeovery]

Stage 3 of the render-surfaces programme (design log: #489; base: #491). The task-gate family plus the D5 phase tree.

Surfaces

• proposed-task — the analysis loop (implementation) and review actions loop carried byte-identical 15-line task displays, approval menus, and auto lines; now one payload surface. Gate mode is a --gate flag rather than an address read — deliberately: one consumer carries the mode in the cycle response, the other in staging-file frontmatter, so the flow owns the mode and the surface owns the form. Per-consumer comment hint (--comment-hint).
• tasks-overview — the proposed-tasks cycle overview both loops shared.
• author-task-gate — planning's per-task authoring menu (scalars as flags; the task detail itself remains a verbatim file emission the flow owns).
• phase-tree — D5 lands: Phase structure — N phases. with numbered phase nodes and wrapped [label, value] tree detail rows through treeList; --approve appends the structure gate. define-phases gets shaped output for the first time (its previous instruction was "present as rendered markdown", freeform).
• task-list --variant existing — plan-construction's twin gate reuses the stage-1 surface: same display, "confirmed" auto phrasing, gated menu without the auto opt-in (matching its existing-tables semantics); its task_list_gate_mode read left the prose.

Five consumer swaps: analysis-loop, review-actions-loop, author-tasks, plan-construction, define-phases.

Test plan

• 13 new tests: byte-exact renders for all four surfaces (incl. the wrapped-detail gutter in the phase tree), gate-flag validation, variant behaviour, loud payload validation.
• npm test — 1496/1496. Typecheck + conventions lint clean.

🤖 Generated with Claude Code

Stack

1. feat(engine): discovery-map add-batch + cache purge at close (D7 one-call) #495
2. feat(engine): render surface catalogue — resume-gate and task-list pilots #490
3. feat(engine): finding + findings-summary surfaces — review-findings loop unified #491
4. feat(engine): task-gate surfaces — proposed-task, tasks-overview, author-task-gate, phase-tree #492 👈 current
5. feat(engine): selection projection + bridge continuation surfaces #493
6. feat(engine): transaction confirmation sections — lifecycle verbs carry their own chrome #496
7. feat(engine): entry-gate + phase-note — entry validation derives engine-side #497
8. feat(engine): the fence is the frame — boxedFrame retired (D8) #498
9. feat(engine): topic complete + discovery-session close fold their kb warnings (7a) #499
10. feat(engine): resume-gate variants + entry-gate --own + phase-completed --paths (7b) #500
11. test(conventions): templated-fence ratchet — check 13 lands D4 (7c) #501