fix(arch): unify TS/Rust types + classroom persistence registration + approval audit

- M11-03: Register ClassroomPersistence via Tauri .setup() hook with
  in-memory fallback. Previously missing — classroom commands would crash at runtime.
- M3-02: Document BrowserHand as schema validator + TypeScript delegation
  passthrough (dual-path architecture explicitly documented).
- M4-04: Add defense-in-depth audit logging in execute_hand() and
  execute_hand_with_source() when needs_approval hands bypass approval gate.
- TYPE-01: Add #[serde(rename_all = "camelCase")] to Rust AgentInfo.
  Add missing fields to TS AgentInfo (messageCount, createdAt, updatedAt).
  Fix KernelStatus TS interface to match Rust KernelStatusResponse
  (baseUrl/model instead of defaultProvider/defaultModel).
- SEC2-P1-01: Document EXTRACTION_DRIVER OnceCell as legacy path;
  Kernel struct field is the active path.
- TriggerSource: Add #[derive(PartialEq)] for approval audit comparisons.

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

@@ -227,28 +227,37 @@ impl LlmDriverForExtraction for TauriExtractionDriver {
     }
 }
 
-/// Global extraction driver instance (lazy-initialized).
+/// Global extraction driver instance (legacy path, kept for compatibility).
+///
+/// **Architecture note:** The Kernel struct now holds its own `extraction_driver` field
+/// (set via `kernel.set_extraction_driver()`), which is the primary path used by
+/// the middleware chain. This OnceCell global is a legacy artifact — its accessors
+/// are dead code. The `configure_extraction_driver()` function is still called during
+/// kernel_init for backward compatibility but the primary consumption path is
+/// through the Kernel struct.
 static EXTRACTION_DRIVER: tokio::sync::OnceCell<Arc<TauriExtractionDriver>> =
     tokio::sync::OnceCell::const_new();
 
-/// Configure the global extraction driver.
+/// Configure the global extraction driver (legacy path).
 ///
-/// Call this during kernel initialization after the Kernel's LLM driver is available.
+/// Called during kernel initialization. The primary path is via
+/// `kernel.set_extraction_driver()` which stores the driver in the Kernel struct
+/// for use by the middleware chain.
 pub fn configure_extraction_driver(driver: Arc<dyn LlmDriver>, model: String) {
     let adapter = TauriExtractionDriver::new(driver, model);
     let _ = EXTRACTION_DRIVER.set(Arc::new(adapter));
-    tracing::info!("[ExtractionAdapter] Extraction driver configured");
+    tracing::info!("[ExtractionAdapter] Extraction driver configured (legacy OnceCell path)");
 }
 
-/// Check if the extraction driver is available.
+/// Check if the extraction driver is available (legacy OnceCell path).
 #[allow(dead_code)]
 pub fn is_extraction_driver_configured() -> bool {
     EXTRACTION_DRIVER.get().is_some()
 }
 
-/// Get the global extraction driver.
+/// Get the global extraction driver (legacy OnceCell path).
 ///
-/// Returns `None` if not yet configured via `configure_extraction_driver`.
+/// Prefer accessing via `kernel.extraction_driver()` when the Kernel is available.
 #[allow(dead_code)]
 pub fn get_extraction_driver() -> Option<Arc<TauriExtractionDriver>> {
     EXTRACTION_DRIVER.get().cloned()