feat(8.0): brain.fillSubtypes migration helper + pre-RC1 gap closure

- brain.fillSubtypes(rules): idempotent subtype back-fill for pre-8.0 data.
  One rule per NounType/VerbType (literal default or per-entry function);
  fills only entries still missing a subtype through the public update()/
  updateRelation() paths; returns { scanned, filled, skipped, errors, byType }.
  Full unit suite in tests/unit/brainy/fill-subtypes.test.ts.
- Fix getNouns/getVerbs pagination hasMore (peek one past the window) —
  was permanently false, silently truncating every multi-page walk.
- find({ near }) without near.id now throws a teaching error instead of an
  opaque storage sharding failure; CLI --threshold without --near applies a
  plain score floor.
- CLI init/close audit: every one-shot command init()s, close()s, and exits
  explicitly; delete the unmaintained interactive REPL; replace the cloud-era
  storage subcommands with status/batch-delete; new types/validate commands.
- requireSubtype JSDoc now documents the 8.0 default-on contract; audit()
  recommendation points at fillSubtypes.
- Docs: data-storage-architecture rewritten to the real 8.0 on-disk layout;
  README storage section reflects filesystem+memory and snapshots; eli5 and
  SEMANTIC_VFS /as-of/ semantics corrected; internal tracker IDs and
  .strategy references scrubbed from published files.

RELEASES.md

@@ -167,8 +167,12 @@ this rename; only the API surface moved.
   Escape hatches: `requireSubtype: false` (last-resort opt-out for legacy
   data) or `requireSubtype: { except: [NounType.Thing, ...] }` (per-type
   allowlist). Per-type rules registered via `brain.requireSubtype(type, opts)`
-  still compose. `brain.audit()` reports entries missing a subtype and
-  `brain.migrateField()` backfills them.
+  still compose. `brain.audit()` reports entries missing a subtype and the new
+  `brain.fillSubtypes(rules)` migration helper backfills them — one rule per
+  NounType/VerbType (literal default or per-entry function), applied only to
+  entries still missing a subtype, returning
+  `{ scanned, filled, skipped, errors, byType }`. Idempotent: re-running fills
+  nothing, so a crashed run is resumed by running it again.
 - **Verb ids are Brainy-generated UUIDs — by contract.** `relate()` now throws
   a teaching error if a caller passes an `id` field
   (`src/utils/paramValidation.ts:526`). In 7.x a supplied id was silently
@@ -270,8 +274,10 @@ The full cost model is in
    `getHistory` / `streamHistory` / `versions` / `data()` per the table above.
 6. **Subtypes:** if your data predates subtype discipline, start with
    `requireSubtype: false`, run `brain.audit()`, backfill with
-   `brain.migrateField()`, then remove the opt-out so the 8.0 default
-   enforcement protects you going forward.
+   `brain.fillSubtypes(rules)` (one rule per type — a literal default or a
+   function deriving the subtype from each entry), re-run `audit()` until
+   `total === 0`, then remove the opt-out so the 8.0 default enforcement
+   protects you going forward.
 7. **CLI scripts:** `fork` / `branch` / `checkout` / `migrate` →
    `snapshot <path>` / `restore <path>` / `history` / `generation`.
 8. **Plugin authors:** apply the contract renames and the BigInt graph
@@ -553,8 +559,7 @@ alongside every other metadata field on the existing write paths.
 `_rev`, `ifRev`, `RevisionConflictError`, and `ifAbsent` all survive the 8.0 Db
 redesign unchanged. 8.0 layers `brain.transact(tx, { ifAtGeneration })` for
 whole-tx CAS on top of the same per-entity mechanism — per-entity for single-record
-patterns, generation-based for "did the world move under me." See
-`.strategy/BRAINY-8.0-SUBTYPE-CONTRACT.md` § C-6 (internal).
+patterns, generation-based for "did the world move under me."
 
 ---
 
@@ -672,8 +677,7 @@ in `validateFindParams()`, both fire before any storage/index/Cortex call. Corte
 
 The new `docs/guides/find-limits.md` calls out that 8.0's Datomic-style `Db.find()`
 may tighten per-call limits; that's a Brainy 8.0 / Cortex 3.0 coordination point
-documented in `.strategy/BRAINY-8.0-SUBTYPE-CONTRACT.md` (open question #4 covers
-the rollout staging, which now also applies to query limits).
+whose rollout staging now also covers query limits.
 
 ### What consumers should do
 
@@ -830,8 +834,7 @@ Brainy before any native call.
 
 - **Native `audit()` proxy.** For billion-scale brains, `audit()` walks every entity (O(N)).
   A native implementation reading from a "null-subtype" bitmap in the column store would be
-  O(buckets). Listed as the 6th open question in the
-  [Brainy 8.0 spec doc](`/media/dpsifr/storage/home/Projects/brainy/.strategy/BRAINY-8.0-SUBTYPE-CONTRACT.md`).
+  O(buckets).
 - **Strict-mode parity test.** Cortex should mirror Brainy's new
   `tests/integration/strict-mode-self-test.test.ts` against their native paths to catch any
   latent bug where native writes bypass JS validation.