refactor(mcp): switch to user-level config ~/.claude.json and remove project-level logic

- Read/write ~/.claude.json (preserve unknown fields) for mcpServers
- Remove settings.local.json and mcp.json handling
- Drop enableAllProjectMcpServers command and UI toggle
- Update types, Tauri APIs, and MCP panel to reflect new status fields
- Keep atomic write and command validation behaviors

src/types.ts

@@ -65,10 +65,7 @@ export interface McpServer {
 
 // MCP 配置状态
 export interface McpStatus {
-  settingsLocalPath: string;
-  settingsLocalExists: boolean;
-  enableAllProjectMcpServers: boolean;
-  mcpJsonPath: string;
-  mcpJsonExists: boolean;
+  userConfigPath: string;
+  userConfigExists: boolean;
   serverCount: number;
 }