refactor: use typed window.metonaDesktop instead of (window as any)

Replaced all '(window as any).metonaDesktop' with the properly typed
'window.metonaDesktop' across mcp-client.ts, skill-manager.ts,
agent-engine.ts, and log-service.ts. The MetonaDesktopAPI type is
already declared in types.d.ts, so the 'as any' cast was unnecessary
and bypassed type checking.

src/renderer/services/agent-engine.ts

@@ -170,7 +170,7 @@ function parseToolCallsFromText(content: string): ToolCall[] {
 
 /** v4.2: 从对话中自动推断用户画像 */
 async function inferUserProfile(userMsg: string, assistantMsg: string): Promise<void> {
-  const bridge = (window as any).metonaDesktop;
+  const bridge = window.metonaDesktop;
   if (!bridge?.db?.getSetting) return;
 
   const profile: Record<string, unknown> = await bridge.db.getSetting('user_profile', {}) || {};
@@ -365,7 +365,7 @@ export interface AgentCallbacks {
 /** 保存执行轨迹到 SQLite */
 async function saveTrace(trace: Omit<TraceEntry, 'id' | 'createdAt'>): Promise<void> {
   try {
-    const bridge = (window as any).metonaDesktop;
+    const bridge = window.metonaDesktop;
     if (!bridge?.db) return;
     const entry = {
       id: `trace_${generateId()}`,