feat: add confidence/weight to Entity and flatten Result fields for convenient access

Add confidence and weight properties to Entity interface and flatten Result fields to top level for improved developer experience and API consistency.

Breaking Changes: None (all changes are backward compatible)

Phase 2 - Entity Confidence & Weight:
- Add confidence (type classification certainty) and weight (entity importance) to Entity interface
- Add confidence/weight parameters to AddParams and UpdateParams
- Update convertNounToEntity() to extract confidence/weight from storage
- Update add() and update() methods to preserve confidence/weight in metadata
- Enable developers to specify and access entity confidence/weight scores

Phase 3 - Result Field Flattening:
- Flatten commonly-used entity fields (type, metadata, data, confidence, weight) to Result top level
- Add createResult() helper for consistent Result construction
- Update all find() code paths to use createResult()
- Enable direct access: result.metadata instead of result.entity.metadata
- Preserve full entity in result.entity for backward compatibility

VFS Fix (from previous work):
- Fix VFSStructureGenerator to use brain.vfs() cached instance instead of creating separate instance
- Improve VFS error messages with step-by-step guidance
- Update examples to show correct vfs.init() usage
- Add comprehensive VFS import verification tests

Documentation Updates:
- Update API_REFERENCE.md with confidence/weight examples and flattened Result documentation
- Enhance JSDoc for add(), get(), find(), similar() with v4.3.0 examples
- Document Result structure changes and backward compatibility
- Add migration examples showing both old and new access patterns

Tests:
- Add 16 comprehensive tests for Entity confidence/weight exposure
- Add tests for Result field flattening
- Add tests for backward compatibility
- All tests passing (16/16)

API Consistency:
- Entity: direct access to confidence/weight
- Result: flattened fields + nested entity (both work)
- Relation: already had confidence/weight (consistent)
- VFS: inherits from Entity (automatic)

Files Changed:
- src/types/brainy.types.ts - Updated Entity, AddParams, UpdateParams, Result interfaces
- src/brainy.ts - Updated implementation and JSDoc for all affected methods
- tests/integration/entity-confidence-weight.test.ts - 16 comprehensive tests
- docs/API_REFERENCE.md - Updated with v4.3.0 examples
- src/importers/VFSStructureGenerator.ts - VFS fix
- src/vfs/VirtualFileSystem.ts - Improved error messages
- examples/unified-import-example.ts - Added vfs.init() example
- tests/integration/vfs-*-verification.test.ts - VFS verification tests

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/types/brainy.types.ts

@@ -22,6 +22,8 @@ export interface Entity<T = any> {
   createdAt: number
   updatedAt?: number
   createdBy?: string
+  confidence?: number  // Type classification confidence (0-1)
+  weight?: number      // Entity importance/salience (0-1)
 }
 
 /**
@@ -59,11 +61,26 @@ export interface RelationEvidence {
 
 /**
  * Search result with similarity score
+ *
+ * Flattens commonly-used entity fields to top level for convenience,
+ * while preserving full entity in 'entity' field for backward compatibility.
  */
 export interface Result<T = any> {
+  // Search metadata
   id: string
   score: number
+
+  // Convenience: Common entity fields flattened to top level
+  type?: NounType      // Entity type (from entity.type)
+  metadata?: T         // Entity metadata (from entity.metadata)
+  data?: any           // Entity data (from entity.data)
+  confidence?: number  // Type classification confidence (from entity.confidence)
+  weight?: number      // Entity importance (from entity.weight)
+
+  // Full entity (preserved for backward compatibility)
   entity: Entity<T>
+
+  // Score transparency
   explanation?: ScoreExplanation
 }
 
@@ -90,6 +107,8 @@ export interface AddParams<T = any> {
   id?: string                  // Optional custom ID
   vector?: Vector              // Pre-computed vector (skip embedding)
   service?: string             // Multi-tenancy support
+  confidence?: number          // Type classification confidence (0-1)
+  weight?: number              // Entity importance/salience (0-1)
 }
 
 /**
@@ -102,6 +121,8 @@ export interface UpdateParams<T = any> {
   metadata?: Partial<T>        // Metadata to update
   merge?: boolean             // Merge or replace metadata (default: true)
   vector?: Vector             // New pre-computed vector
+  confidence?: number          // Update type classification confidence
+  weight?: number              // Update entity importance/salience
 }
 
 /**