fix: resolve medium/low audit findings across backend and frontend

- ctx CLI: validate int() limit arg, wrap FTS5 MATCH in try/except
- ctx.rs: FTS5 error message clarity, Mutex::lock() returns Err not panic
- sdk-messages.ts: runtime type guards (str/num) replace bare `as` casts
- agent-runner.ts: strip ANTHROPIC_* env vars alongside CLAUDE*
- agent-dispatcher.ts: timestamps use seconds (match session.rs convention)
- remote.rs: disconnect handler uses lock().await not try_lock()
- session.rs: propagate pane_ids serialization error
- watcher.rs: reject root-level paths instead of silent no-op
- lib.rs: log warnings on profile.toml read failure and resource_dir error
- agent-bridge.ts: validate event payload is object before cast

v2/src-tauri/src/watcher.rs

@@ -72,8 +72,10 @@ impl FileWatcherManager {
         )
         .map_err(|e| format!("Failed to create watcher: {e}"))?;
 
+        let watch_dir = file_path.parent()
+            .ok_or_else(|| format!("Cannot watch root-level path: {path}"))?;
         watcher
-            .watch(file_path.parent().unwrap_or(&file_path), RecursiveMode::NonRecursive)
+            .watch(watch_dir, RecursiveMode::NonRecursive)
             .map_err(|e| format!("Failed to watch path: {e}"))?;
 
         let mut watchers = self.watchers.lock().unwrap();