fix: resolve clear() not deleting COW data and counters

Fixes critical bug where brain.clear() did not fully clear storage:

Root causes:
1. _cow/ directory contents deleted but directory not removed
2. In-memory counters (totalNounCount, totalVerbCount) not reset
3. COW could auto-reinitialize on next operation

Fixes applied:
- FileSystemStorage: Delete entire _cow/ directory with fs.rm()
- OPFSStorage: Delete _cow/ with removeEntry({recursive: true})
- S3CompatibleStorage: Reset counters after clear
- BaseStorage: Guard initializeCOW() against reinit when cowEnabled=false
- All adapters: Reset totalNounCount and totalVerbCount to 0

Impact: Resolves Workshop bug report - storage now properly clears from
103MB to 0 bytes, entity counts correctly return to 0.

GCSStorage, R2Storage, AzureBlobStorage already had correct implementations.

src/storage/baseStorage.ts

@@ -289,6 +289,12 @@ export abstract class BaseStorage extends BaseStorageAdapter {
     branch?: string
     enableCompression?: boolean
   }): Promise<void> {
+    // v5.6.1: If COW was explicitly disabled (e.g., via clear()), don't reinitialize
+    // This prevents automatic recreation of COW data after clear() operations
+    if (this.cowEnabled === false) {
+      return
+    }
+
     // Check if RefManager already initialized (full COW setup complete)
     if (this.refManager) {
       return