feat: v0.49 - Filter discovery API, remove deprecated methods, improve performance

BREAKING CHANGES:
- Removed deprecated getAllNouns() and getAllVerbs() methods
- All internal usage migrated to pagination-based methods

New Features:
- Filter Discovery API:
  - getFilterValues(field): Get all available values for a field
  - getFilterFields(): Get all filterable fields
  - Enables dynamic filter UI generation with O(1) field discovery
- Hybrid metadata indexing with field-level indexes
- Adaptive auto-flush for optimal performance
- LRU caching for metadata indexes

Improvements:
- Fixed ENAMETOOLONG errors from vector-based filenames
- Safe filename generation using hash-based approach
- Scalable chunked value storage for millions of entries
- Performance optimization with adaptive flush thresholds
- Added support for $includes operator in metadata filters

Technical:
- Replaced vector-based filenames with safe hash approach
- Implemented MetadataIndexCache with existing SearchCache pattern
- Field indexes enable O(1) filter discovery
- Adaptive flush based on performance metrics (20-200 entries)
- All tests passing with improved metadata filtering

src/storage/adapters/opfsStorage.ts

@@ -255,46 +255,6 @@ export class OPFSStorage extends BaseStorage {
     }
   }
 
-  /**
-   * Get all nouns from storage
-   */
-  protected async getAllNouns_internal(): Promise<HNSWNoun_internal[]> {
-    await this.ensureInitialized()
-
-    const allNouns: HNSWNoun_internal[] = []
-    try {
-      // Iterate through all files in the nouns directory
-      for await (const [name, handle] of this.nounsDir!.entries()) {
-        if (handle.kind === 'file') {
-          try {
-            // Read the noun data from the file
-            const file = await safeGetFile(handle)
-            const text = await file.text()
-            const data = JSON.parse(text)
-
-            // Convert serialized connections back to Map<number, Set<string>>
-            const connections = new Map<number, Set<string>>()
-            for (const [level, nounIds] of Object.entries(data.connections)) {
-              connections.set(Number(level), new Set(nounIds as string[]))
-            }
-
-            allNouns.push({
-              id: data.id,
-              vector: data.vector,
-              connections,
-              level: data.level || 0
-            })
-          } catch (error) {
-            console.error(`Error reading noun file ${name}:`, error)
-          }
-        }
-      }
-    } catch (error) {
-      console.error('Error reading nouns directory:', error)
-    }
-
-    return allNouns
-  }
 
   /**
    * Get nouns by noun type (internal implementation)
@@ -469,12 +429,6 @@ export class OPFSStorage extends BaseStorage {
     }
   }
 
-  /**
-   * Get all verbs from storage (internal implementation)
-   */
-  protected async getAllVerbs_internal(): Promise<HNSWVerb[]> {
-    return this.getAllEdges()
-  }
 
   /**
    * Get all edges from storage