fix(critical): enable metadata indexing in write-only mode + force buffering activation

🚨 CRITICAL FIXES:

1. METADATA INDEXING IN WRITE-ONLY MODE:
   - Was: if (\!this.writeOnly) - DISABLED metadata indexing for bluesky/github packages\!
   - Now: if (\!this.readOnly) - ENABLES metadata indexing in write-only mode
   - Fixes all conditional checks to allow write-only mode indexing
   - Write-only mode NEEDS metadata indices for search capability\!

2. STATISTICS FOLDER LOCATION:
   - Statistics now go to _system/ folder instead of legacy _index/
   - Uses systemPrefix instead of indexPrefix for new statistics

3. FORCE BUFFERING ACTIVATION:
   - Threshold lowered from 1 to 0 (immediate activation)
   - Added 'true' condition to force enable high-volume mode
   - This should guarantee buffering activation in production

IMPACT:
- bluesky-package and github-package will now CREATE metadata indices
- _metadata/noun/ and _metadata/verb/ folders will appear in S3
- Metadata filtering and field searches will work in write-only mode
- Statistics will be in proper _system/ folder structure
- Buffering should activate immediately (guaranteed)

This fixes the missing S3 folder structure and search capabilities.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@soulcraft/brainy",
-  "version": "0.54.2",
+  "version": "0.54.3",
   "description": "A vector graph database using HNSW indexing with Origin Private File System storage",
   "main": "dist/index.js",
   "module": "dist/index.js",