feat(intelligence): add personality detector — auto-adjust from conversation signals

- PersonalityConfig with 4 dimensions: tone, proactiveness, formality, humor
- Signal detection from Chinese user messages (e.g. "说简单点" → Simple tone)
- apply_personality_adjustments() returns new immutable config
- build_personality_prompt() injects personality into system prompts
- Integrated into post_conversation_hook for automatic detection
- In-memory persistence via OnceLock (VikingStorage integration TODO)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

desktop/src-tauri/src/intelligence/mod.rs

@@ -34,6 +34,7 @@ pub mod validation;
 pub mod extraction_adapter;
 pub mod pain_aggregator;
 pub mod solution_generator;
+pub mod personality_detector;
 
 // Re-export main types for convenience
 pub use heartbeat::HeartbeatEngineState;