feat: brain.get() metadata-only optimization - Phase 2 (testing)

Fixed convertMetadataToEntity() to properly extract custom metadata fields
using same destructuring pattern as baseStorage.getNoun(). This ensures
metadata is correctly populated in metadata-only entities.

Test Updates:
- Fixed unit tests to add { includeVectors: true } where vectors are checked
- Created comprehensive brain.get() optimization tests (11 tests, all passing)
- Created VFS performance integration tests
- Fixed invalid NounType references (NounType.Place → NounType.Location)
- Adjusted performance expectations for MemoryStorage (10%+ vs 75%+ for FS)

Files Updated:
- src/brainy.ts: Fixed convertMetadataToEntity() destructuring
- tests/unit/brainy-get-optimization.test.ts: New comprehensive tests
- tests/unit/brainy/get.test.ts: Added includeVectors where needed
- tests/unit/brainy/batch-operations.test.ts: Added includeVectors
- tests/unit/brainy/update.test.ts: Added includeVectors
- tests/unit/brainy/add.test.ts: Added includeVectors (3 tests)
- tests/brainy-3.test.ts: Added includeVectors

tests/unit/brainy/batch-operations.test.ts

@@ -121,9 +121,9 @@ describe('Brainy Batch Operations', () => {
       
       const result = await brain.addMany({ items: entities })
       
-      // All should have vectors
+      // All should have vectors - v5.11.1: Need includeVectors
       for (const id of result.successful) {
-        const entity = await brain.get(id)
+        const entity = await brain.get(id, { includeVectors: true })
         expect(entity?.vector).toBeDefined()
         expect(entity?.vector?.length).toBeGreaterThan(0)
       }