fix: internal subtype consistency + brain.audit() diagnostic + improved enforcement errors

Brainy 7.30 shipped opt-in subtype enforcement; SDK 3.20.0 then registered
SDK_CORE_VOCABULARY on every consumer's brain (Event, Collection, Message,
Contract, Media, Document NounTypes). On 2026-06-08 Venue's /book flow went 500
because their brain.add({ type: NounType.Event, ... }) call sites lacked
subtype. An audit of Brainy's OWN source revealed 14 HIGH-risk internal write
paths that also omit subtype — any consumer running the same vocabulary would
have hit Brainy's infrastructure paths next. 7.30.1 closes both gaps before
8.0 makes strict mode the default.

Additive across the board. Zero behavior change for consumers not using strict
mode. Every change is JS-side — Cortex needs no work for 7.30.1.

NEW — brain.audit() diagnostic
- Read-only method walking storage.getNouns() / getVerbs() pagination
- Returns { entitiesWithoutSubtype: { type: count }, relationshipsWithoutSubtype,
  total, scanned, recommendation }
- VFS infrastructure entities excluded by default (they bypass enforcement via
  isVFSEntity marker); pass { includeVFS: true } to surface them
- The companion to migrateField (7.x) and fillSubtypes (8.0): tells consumers
  exactly what would break under strict enforcement, deterministically

NEW — Improved enforcement error messages
- Caller's source location extracted from Error().stack so users see their own
  call site, not a Brainy internal frame
- Specific guidance branches: registered vocabulary → "Pass one of: a, b, c";
  brain-wide strict mode → mentions the except clause; otherwise → registration
  recipe via brain.requireSubtype()
- Documentation link to the canonical migration recipe
- Same shape for noun and verb enforcement

NEW — CLI --subtype flag
- brainy add and brainy relate gain -s/--subtype <value>
- Defaults to 'cli-add' / 'cli-relate' so the CLI works against strict-mode
  brains without the user needing to know the vocabulary in advance

INTERNAL — every Brainy write path now sets subtype
- VFS Contains edges (5 sites at lines 503/905/1694/1772/1886) → 'vfs-contains'
- VFS symlink entity → 'vfs-symlink' (NEW — distinct from 'vfs-file')
- VFS copy-file → preserves source subtype, falls back to 'vfs-file'
- VFS symlink also adopts the isVFSEntity infrastructure marker so it bypasses
  enforcement in strict mode
- Aggregation materializer (Measurement entities) → 'materialized-aggregate'
- ImportCoordinator (3 sites): document → 'import-source'; entities →
  options.defaultSubtype ?? 'imported'; placeholder → 'import-placeholder'
- SmartImportOrchestrator (4 entity sites + 2 batch relate sites): same
  precedence (extractor → options.defaultSubtype → 'imported')
- EntityDeduplicator → candidate.subtype ?? 'imported'
- UniversalImportAPI → extractor → 'extracted' for both entities and relations
- NeuralImport → adds defaultSubtype to NeuralImportOptions; precedence same
- GoogleSheetsIntegration → request body 'subtype' ?? 'imported-from-sheets'
- ODataIntegration → request body 'Subtype' ?? 'imported-from-odata'
- MCP client message storage → 'mcp-message' (also fixes pre-existing missing
  data field and missing type by aliasing from the prior text field)

Side-effect fix: storage.getNouns() paginated now surfaces subtype to top-level
- Single-noun getNoun() already did this in 7.30; the paginated path was missed
- Without this fix brain.audit() saw missing subtype on entities that actually
  had one (caught by the strict-mode self-test before release)

NEW — tests/integration/strict-mode-self-test.test.ts (13 tests)
- Creates a brain under the exact SDK_CORE_VOCABULARY shape Venue hit + brain-
  wide strict mode
- Exercises every internal Brainy path: VFS root + mkdir + writeFile + cp + mv
  + ln + symlink; aggregation engine; audit diagnostic with includeVFS toggle
- Validates error message UX: caller location, vocabulary guidance, brain-wide
  strict mode guidance, off-vocabulary value reporting

Docs
- New "Strict mode in practice" section in docs/guides/subtypes-and-facets.md
  covering the SDK_CORE_VOCABULARY pattern, 4-step migration recipe
  (audit → migrateField → hand-fix → re-audit), the Brainy-internal label
  reference table, and an 8.0 forward-look on fillSubtypes()
- docs/api/README.md: new audit() entry, strict-mode tips on add() and relate()
- RELEASES.md: full 7.30.1 entry

Cortex parity (forward-looking, not blocking 7.30.1)
- 6th open question added to .strategy/BRAINY-8.0-SUBTYPE-CONTRACT.md: native
  fast path for audit() and fillSubtypes() via column-store null-subtype
  bitmap for billion-scale brains
- Cortex should add a parity test mirroring strict-mode-self-test.test.ts
  against their native paths to catch any latent bug where native writes
  bypass JS validation
- Brainy-internal subtype labels become a documented part of the 8.0 contract
  (useful for Cortex telemetry surfacing Brainy-managed infrastructure %)

Verification
- npx tsc --noEmit: clean
- npm test: 1468/1468 unit
- 7.29 noun integration suite: 26/26 (no regression)
- 7.30 verb subtype + enforcement integration suite: 30/30 (no regression)
- New strict-mode-self-test integration suite: 13/13
- npm run build: clean
- Closed-source product reference audit: clean

Addresses VE-SUBTYPE-MIGRATION (Venue's reported request) and ships internal
labels Venue did NOT ask for but that would have broken them next under their
own vocabulary registration.

src/storage/baseStorage.ts

@@ -1479,10 +1479,14 @@ export abstract class BaseStorage extends BaseStorageAdapter {
                   }
                 }
 
-                // Combine noun + metadata
+                // Combine noun + metadata. Subtype is surfaced to top-level here
+                // (mirrors what `getNoun()` already does) so callers — including
+                // the 7.30.1 `brain.audit()` diagnostic — see a consistent shape
+                // regardless of which getter path they reach.
                 collectedNouns.push({
                   ...deserialized,
                   type: (metadata.noun || 'thing') as NounType,
+                  subtype: (metadata as any).subtype as string | undefined,
                   confidence: metadata.confidence,
                   weight: metadata.weight,
                   createdAt: metadata.createdAt