feat(mcp): use project config as SSOT and sync enabled servers to ~/.claude.json

- Add McpConfig to MultiAppConfig and persist MCP servers in ~/.cc-switch/config.json
- Add Tauri commands: get_mcp_config, upsert_mcp_server_in_config, delete_mcp_server_in_config, set_mcp_enabled, sync_enabled_mcp_to_claude, import_mcp_from_claude
- Only write enabled MCPs to ~/.claude.json (mcpServers) and strip UI-only fields (enabled/source)
- Frontend: update API wrappers and MCP panel to read/write via config.json; seed presets on first open; import from ~/.claude.json
- Fix warnings (remove unused mut, dead code)
- Verified with cargo check and pnpm typecheck

src-tauri/src/lib.rs

@@ -1,6 +1,7 @@
 mod app_config;
 mod claude_plugin;
 mod claude_mcp;
+mod mcp;
 mod codex_config;
 mod commands;
 mod config;
@@ -428,6 +429,13 @@ pub fn run() {
             commands::upsert_claude_mcp_server,
             commands::delete_claude_mcp_server,
             commands::validate_mcp_command,
+            // New MCP via config.json (SSOT)
+            commands::get_mcp_config,
+            commands::upsert_mcp_server_in_config,
+            commands::delete_mcp_server_in_config,
+            commands::set_mcp_enabled,
+            commands::sync_enabled_mcp_to_claude,
+            commands::import_mcp_from_claude,
             // ours: endpoint speed test + custom endpoint management
             commands::test_api_endpoints,
             commands::get_custom_endpoints,