feat(engine): discovery-map add-batch + cache purge at close (D7 one-call)

[leeovery]

Stage 5a of the render-surfaces programme (design log: #489; base: #493) — the first two D7 deliveries.

discovery-map add-batch

engine discovery-map add-batch <wu> --file <topics.json> — the whole harvest in one transaction. Entries {name, routing, summary, description?, brief_path?, force_dismissed?}; all validation runs before anything applies (illegal name, unknown routing, collision, dismissed-without-force, in-batch duplicate → loud error, zero writes — never a partial map). brief_path rides on the entry, so the per-topic manifest set follow-up dies with the loop: the fumi harvest's 48 sequential calls (24 adds + 24 sets, the run that produced the $E aliasing incident) become one call. confirm-and-persist.md swaps to payload + single call, and its zsh-quoting caveats leave with the argv.

Cache purge at work-unit close

workunit complete / cancel / absorb remove .workflows/.cache/{wu}/ wholesale — cache is work-unit-lifetime scratch (survives context refresh during active work, garbage at close). Disk-only (gitignored), and reactivation-safe: purging is what protects reopened gates from stale tracking files.

Test plan

• add-batch: happy path (brief_path recorded, source pinned to discovery, map_total), atomicity under mid-batch collision (state byte-compared before/after), per-entry force_dismissed + refusal, six loud validation cases, payload-read failure.
• purge: complete purges own cache and leaves siblings; cancel purges; absorb purges the absorbed feature's cache.
• npm test — 1508/1508. Typecheck + conventions lint clean.

The two call-chain audit reports (15 further repeated-call sites; the shell-construction cluster) are recorded in the design log for stage 5b scoping.

🤖 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): discovery-map add-batch + cache purge at close (D7 one-call) #495 👈 current

[leeovery]

Closed per review: built backwards — the batch contract must be designed census-first from the full audit (16 sites, two reports — recorded in design/render-surfaces.md) before any instance is implemented, and the cache purge was an unrelated change conflated in. Both return after the render stack lands: batching as its own census-first programme, the purge as a standalone PR.