feat(ux): human-readable titles — UX-1 of the work-topology plan

[kevintseng]

UX-1: human-readable titles (work-topology plan, PR 1 of 6)

Entities gain a nullable title column — the string a human (or agent) reads first. name keeps its identity as the stable machine dedup/append key and is no longer used as display anywhere.

Write side

• ALTER-only migration in both schema owners (src/db.ts + the hook mirror in scripts/hooks/_shared.js). check-schema-drift.mjs cannot see ALTER blocks, so each side carries a comment locking it to the other.
• All three write hooks generate heuristic titles via shared truncateTitle (120 chars): commit subject verbatim (post-commit), date+project+verb (session-summary, pre-compact). The weekly-summary compressor — the fourth entity-creation path — titles its digest rows too.
• Every machine-generated title is stamped metadata.title_source='heuristic'. An unmarked title is treated as human-provided and permanent; the mark is what lets a future LLM titling pass (dreamer backfill) know what it may replace.
• remember() / MCP / HTTP / CLI accept an optional title through the one shared Zod schema. Blank-after-sanitize collapses to undefined (= leave an existing title untouched — the namespace rule). CLI quick capture titles the memory with its own positional text.

Search side

• entities_fts stays two-column: the title is folded into the observations feed by one private helper that both insertFtsRow and removeFromFts call, so a contentless delete can never build its match text differently from the insert that created the row.
• The archived LIKE supplement matches e.title too — a memory findable by its title while active stays findable once archived.
• One-time, fill-only, marker-keyed backfill (title_backfill_v1, modeled on the signal-score pass) titles pre-existing rows and reindexes what it titles — active rows only: archived rows have no FTS entry, and a contentless delete for text never indexed is itself the corruption.

Display side

• displayTitle() in entity-display.ts is the single fallback chain: title → pickBestObservation → typeLabel+date — never name.
• MemoryRow headline prefers the title; the raw-name meta span is removed (name survives as the headline's tooltip). LessonsTab cards, ProjectRoadmap rails/phase anchors/mindmap labels all route through the same helper. Browse/Lessons filter haystacks include the title so filtering by the visible headline matches.

Verification (all run at HEAD, this branch)

測試: node scripts/run-tests-isolated.mjs → exit=0
      Test Files 129 passed (129) / Tests 2024 passed (2024)   (main 基線: 1997/128)
typecheck: exit=0
verify:release: exit=0 (lint, version/mirror/doc-claims, audit, consumer advisories)

Mutation break-tests (all KILLED — two only after strengthening a vacuous probe)

1. Backfill reindex deleted → survived the first probe: kg.search()'s status='active' JOIN hid the stale FTS tokens the raw index still held (delete failed with "database disk image is malformed" on stderr while the test stayed green). Probe rewritten against raw entities_fts MATCH → KILLED.
2. Hook-side delete without previousTitle → KILLED by both the captureEntity symmetry test and the new mirror-parity title-fold case.
3. Archived LIKE title arm removed → survived the backfill-derived fixture (backfilled titles ⊆ observations, so the o.content arm masks the title arm). New isolating test with a manual title whose token appears nowhere else → KILLED.

Audit baseline

UX-1's insertions shifted 18 line-keyed C5 entries — re-keyed with each statement verified at its new line, classifications unchanged. cli.ts needed collision-safe ordering (:171→:177 lands on the key :177→:183 vacates — the wrong-sibling hazard the 2026-08-13 note in those entries warns about). Two new C1 hits triaged: mirror-parity got a genuine count pin; db.test.ts's .toBe(0) is PRAGMA notnull flag equality, baselined with that reason.

Out of scope (per the reviewed plan)

LLM-generated titles (dreamer backfill, next), status/enum work (display-derived only), work-layer type whitelist (UX-4), M0 measurements.