fix(desktop): prevent transformCallback crash in browser mode

Root cause: ChatArea.tsx called listen() from @tauri-apps/api/event
directly on component mount without checking isTauriRuntime(). When
accessed from a regular browser (not Tauri WebView), window.__TAURI_INTERNALS__
is undefined, causing "Cannot read properties of undefined (reading 'transformCallback')".

Solution:
- Created lib/safe-tauri.ts with safe wrappers (safeInvoke, safeListen,
  safeListenEvent, requireInvoke) that gracefully degrade when Tauri
  IPC is unavailable
- Replaced direct listen() call in ChatArea.tsx with safeListenEvent()

desktop/src/components/ChatArea.tsx

@@ -7,7 +7,8 @@ import { useArtifactStore } from '../store/chat/artifactStore';
 import { useConnectionStore } from '../store/connectionStore';
 import { useAgentStore } from '../store/agentStore';
 import { useConfigStore } from '../store/configStore';
-import { listen, type UnlistenFn } from '@tauri-apps/api/event';
+import { type UnlistenFn } from '@tauri-apps/api/event';
+import { safeListenEvent } from '../lib/safe-tauri';
 import { Paperclip, SquarePen, ArrowUp, MessageSquare, Download, X, FileText, Image as ImageIcon } from 'lucide-react';
 import { Button, EmptyState, MessageListSkeleton, LoadingDots } from './ui';
 import { ResizableChatLayout } from './ai/ResizableChatLayout';
@@ -160,7 +161,7 @@ export function ChatArea() {
   // Listen for hand-execution-complete Tauri events
   useEffect(() => {
     let unlisten: UnlistenFn | undefined;
-    listen<{ approvalId: string; handId: string; success: boolean; error?: string | null }>(
+    safeListenEvent<{ approvalId: string; handId: string; success: boolean; error?: string | null }>(
       'hand-execution-complete',
       (event) => {
         const { handId, success, error } = event.payload;

desktop/src/lib/safe-tauri.ts

@@ -0,0 +1,104 @@
+/**
+ * Safe Tauri API Wrappers
+ *
+ * All Tauri APIs (invoke, listen, etc.) depend on `window.__TAURI_INTERNALS__`
+ * which only exists inside the Tauri WebView. When the frontend is accessed
+ * from a regular browser (e.g. http://localhost:1420/ for debugging), these
+ * APIs throw cryptic errors like:
+ *
+ *   TypeError: Cannot read properties of undefined (reading 'transformCallback')
+ *
+ * This module provides drop-in replacements that gracefully degrade when
+ * the Tauri runtime is not available.
+ */
+
+import { isTauriRuntime } from './tauri-gateway';
+import { createLogger } from './logger';
+
+const log = createLogger('safe-tauri');
+
+// ---------------------------------------------------------------------------
+// Types
+// ---------------------------------------------------------------------------
+
+export type { UnlistenFn } from '@tauri-apps/api/event';
+
+// ---------------------------------------------------------------------------
+// Safe invoke
+// ---------------------------------------------------------------------------
+
+/**
+ * Type-safe wrapper around Tauri `invoke`.
+ * Returns `null` (with a debug log) when not in Tauri runtime.
+ */
+export async function safeInvoke<T>(
+  cmd: string,
+  args?: Record<string, unknown>,
+): Promise<T | null> {
+  if (!isTauriRuntime()) {
+    log.debug(`invoke("${cmd}") skipped — not in Tauri runtime`);
+    return null;
+  }
+
+  const { invoke } = await import('@tauri-apps/api/core');
+  return invoke<T>(cmd, args);
+}
+
+/**
+ * Like `safeInvoke` but throws when not in Tauri runtime.
+ * Use for operations that MUST have a Tauri backend.
+ */
+export async function requireInvoke<T>(
+  cmd: string,
+  args?: Record<string, unknown>,
+): Promise<T> {
+  if (!isTauriRuntime()) {
+    throw new Error(`invoke("${cmd}") failed — not running in Tauri WebView`);
+  }
+
+  const { invoke } = await import('@tauri-apps/api/core');
+  return invoke<T>(cmd, args);
+}
+
+// ---------------------------------------------------------------------------
+// Safe listen
+// ---------------------------------------------------------------------------
+
+/**
+ * Wrapper around Tauri `listen`.
+ * Returns a no-op `UnlistenFn` when not in Tauri runtime.
+ *
+ * Usage — replace:
+ *   import { listen } from '@tauri-apps/api/event';
+ * With:
+ *   import { safeListen } from '../lib/safe-tauri';
+ */
+export async function safeListen<T>(
+  event: string,
+  handler: (payload: T) => void,
+): Promise<() => void> {
+  if (!isTauriRuntime()) {
+    log.debug(`listen("${event}") skipped — not in Tauri runtime`);
+    return () => {};
+  }
+
+  const { listen } = await import('@tauri-apps/api/event');
+  return listen<T>(event, (e) => handler(e.payload));
+}
+
+/**
+ * Wrapper around Tauri `listen` that provides the full Event object.
+ * Returns a no-op `UnlistenFn` when not in Tauri runtime.
+ */
+export async function safeListenEvent<T>(
+  event: string,
+  handler: (event: { event: string; payload: T }) => void,
+): Promise<() => void> {
+  if (!isTauriRuntime()) {
+    log.debug(`listen("${event}") skipped — not in Tauri runtime`);
+    return () => {};
+  }
+
+  const { listen } = await import('@tauri-apps/api/event');
+  return listen<T>(event, (e) => handler(e));
+}