Release v6.4.0: Dual-tag system, search API improvements, and privacy features

This release introduces powerful new privacy controls and search improvements:

**New Features:**
- Dual-tag system for meta-observation control
  - <private> tags for user-level privacy control
  - <claude-mem-context> tags for system-level auto-injected observations
- Privacy tag documentation and inline help in context hook

**Improvements:**
- Simplified search API parameters to eliminate bracket encoding issues
- Improved user messaging for new privacy features

**Technical:**
- Tag stripping happens at hook layer (edge processing)
- Shared utilities in src/utils/tag-stripping.ts
- Database index optimization for user prompts lookup

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

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

plugin/.claude-plugin/plugin.json

@@ -1,6 +1,6 @@
 {
   "name": "claude-mem",
-  "version": "6.3.7",
+  "version": "6.4.0",
   "description": "Persistent memory system for Claude Code - seamlessly preserve context across sessions",
   "author": {
     "name": "Alex Newman"