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.

docs/architecture/multiprocess-storage-mixin.md

@@ -86,9 +86,8 @@ Benefits:
   `FileSystemStorage` is the only one in-tree, but Cortex's
   `MmapFileSystemStorage` inherits from it — interface relocation would
   ripple through the plugin ecosystem.
-- The current state works. Real failure modes
-  (BR-CX-INTERFACE-GAP) were build/install artifacts, not type-system
-  failures.
+- The current state works. The real failure modes seen in the field
+  were build/install artifacts, not type-system failures.
 - 7.22.0 just shipped a clean fix. Stacking another refactor before
   consumers absorb it adds churn without urgency.
 - The `hasStorageMethod()` guard accomplishes the same runtime safety the