feat(health): the gate reads the named report — reads refuse loudly, never rebuild; open serves before it returns; the ceremony door

The read gate stops consulting the unnamed isReady() boolean: every provider
may expose healthReport() (sync, O(1), composed from exact ledgers —
HealthReport with a monotonic generation, per-invariant source
ledger|deep|unledgered, missing {count, sample}), and one readiness
authority (assessProviderHealth) derives the verdict. Unledgered families
are UNKNOWN — never healthy, never broken; a report that throws is a loud
not-ready, never a shrug. Reads at the four index choke points refuse with
the typed NotReady errors, narrated once per (provider, generation) — a
read NEVER starts a store walk:

- the first-read lazy build retires (open builds instead, regardless of
  size — the ≥10k deferral and the "lazy loading on first query" branch go;
  disableAutoRebuild is re-meant honestly in its docs);
- the verify*Live read-path rebuild triggers retire (refuse-or-serve);
- the read-time consistency probe that could launch a dark rebuild from an
  ordinary find() retires;
- repairIndex({ rebuild: ['metadata'|'graph'|'vector'] | 'all' }) is the
  one explicit door: rebuilds the named leg unconditionally and reports
  rebuilt per family; bare repairIndex() stays report-driven.

test(lifecycle): the biography lane — a store's whole life, refereed

tests/lifecycle/: an independent shadow model referees every read after
every chapter (founding, a working day, clean restart, crash, repair,
second life). Chapters 1-3 green. Chapters 4-6 assert the true contract and
are marked .fails as a release-blocking finding (the kill-matrix
convention): after a crash + adopt reopen the metadata index computes its
'catchup' watermark verdict and nothing consumes it — find() serves the
pre-crash index while canonical and counts recover. The catchup wiring is
the cure; a passing .fails will force the marker's removal. The lane runs
in the integration gate (config + coverage guard).

src/index.ts

@@ -269,6 +269,10 @@ export type { FamilyStamp, StampMembers, StampVerdict } from './db/familyStamp.j
 export { isVersionedIndexProvider } from './plugin.js'
 export type { VersionedIndexProvider } from './plugin.js'
 export type { ProviderInvariantReport, InvariantResult, InvariantHeal } from './plugin.js'
+// The named, synchronous, O(1) health-report contract (the read gate's ONLY
+// source of truth for "can I serve right now") — see HealthReport's
+// derivation laws in plugin.ts.
+export type { HealthReport, LedgerInvariantResult, InvariantSource } from './plugin.js'
 // Optional provider self-report of outstanding background maintenance work
 // (compaction, deferred writes, etc.) — the payload type for
 // brain.maintenanceDebt(). See the measure-only-what-you-track contract on