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/update.test.ts

@@ -139,17 +139,18 @@ describe('Brainy.update()', () => {
         type: 'thing'
       }))
       
-      const original = await brain.get(id)
+      // v5.11.1: Need includeVectors to check vectors
+      const original = await brain.get(id, { includeVectors: true })
       const originalVector = original!.vector
-      
+
       // Act - Update with new data triggers re-embedding
       await brain.update({
         id,
         data: 'Completely different text content'
       })
-      
+
       // Assert
-      const updated = await brain.get(id)
+      const updated = await brain.get(id, { includeVectors: true })
       expect(updated).not.toBeNull()
       // Vector should be different after re-embedding
       expect(updated!.vector).not.toEqual(originalVector)