chore: Release v4.2.1 - Anti-meta-referential prompt improvements

Patch release confirming the effectiveness of prompt engineering changes that prevent meta-referential observations.

Key Improvements (from v4.2.0 prompt work):
- Observations now focus on deliverables shipped, not memory system operations
- Clear distinction between "what was built" vs "what the memory tool processed"
- Contrastive examples prevent pollution like "Processed tool executions"
- Smart handling of edge cases when working ON the memory system itself

Evidence:
Recent context shows progression from meta-referential garbage (10/21 10:48 PM) to excellent deliverable-focused observations (10/21 11:46 PM).

No code changes in this release - just version bump to mark the successful prompt improvements as stable.

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

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

.claude-plugin/marketplace.json

@@ -10,7 +10,7 @@
   "plugins": [
     {
       "name": "claude-mem",
-      "version": "4.1.1",
+      "version": "4.2.1",
       "source": "./plugin",
       "description": "Persistent memory system for Claude Code - context compression across sessions"
     }

package.json

@@ -1,6 +1,6 @@
 {
   "name": "claude-mem",
-  "version": "4.2.0",
+  "version": "4.2.1",
   "description": "Memory compression system for Claude Code - persist context across sessions",
   "keywords": [
     "claude",