feat: Add /pa personal assistant command and state infrastructure

Implement canonical /pa entrypoint for user requests with:
- Context-aware request routing via master-orchestrator
- Session and persistent context level overrides
- Memory system with UUID-based general-instructions.json
- State files for session context and preferences

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

state/personal-assistant/session-context.json

@@ -0,0 +1,6 @@
+{
+  "version": "1.0",
+  "current_context_level": null,
+  "set_at": null,
+  "set_by": null
+}