feat(claude-desktop): add 3P provider switching with proxy gateway

Adds a new ClaudeDesktop AppType that writes Claude Desktop's third-party
inference profile under configLibrary/, sharing _meta.json with other
launchers (Ollama-compatible) so cc-switch can coexist with them.

Two switch modes:
- direct: provider already exposes claude-* / anthropic/claude-* model
  ids on Anthropic Messages, Claude Desktop connects to it directly.
- proxy: cc-switch's local proxy acts as the inference gateway,
  presenting only claude-* route names to Claude Desktop and mapping
  them to real upstream models. Required after Anthropic restricted
  Claude Desktop to claude-family ids.

Backend:
- New module claude_desktop_config with snapshot/rollback, official seed
  bypass, /claude-desktop/v1/{models,messages} routes, and a single
  source of truth for default proxy routes.
- Gateway token persisted in SQLite, validated on every proxied request.
- get_claude_desktop_status surfaces drift signals (stale models,
  missing routes, proxy stopped, base URL mismatch, missing token).

Frontend:
- Slim ClaudeDesktopProviderForm independent from ProviderForm,
  controlled by a top-level appId guard.
- ProviderList banner consumes the status query (5s polling) and
  renders actionable diagnostics.
- ClaudeDesktopRouteToggle in the header to start/stop the local
  gateway without touching takeover state.
- Three-locale i18n synchronised.

src/lib/api/providers.ts

@@ -25,6 +25,28 @@ export interface OpenTerminalOptions {
   cwd?: string;
 }
 
+export interface ClaudeDesktopStatus {
+  supported: boolean;
+  configured: boolean;
+  appliedId?: string | null;
+  profilePath?: string | null;
+  configLibraryPath?: string | null;
+  mode?: "direct" | "proxy" | null;
+  expectedBaseUrl?: string | null;
+  actualBaseUrl?: string | null;
+  proxyRunning: boolean;
+  staleRawModels: boolean;
+  missingRouteMappings: boolean;
+  gatewayTokenConfigured: boolean;
+}
+
+export interface ClaudeDesktopDefaultRoute {
+  routeId: string;
+  envKey: string;
+  displayName: string;
+  supports1m: boolean;
+}
+
 export const providersApi = {
   async getAll(appId: AppId): Promise<Record<string, Provider>> {
     return await invoke("get_providers", { app: appId });
@@ -74,6 +96,18 @@ export const providersApi = {
     return await invoke("import_default_config", { app: appId });
   },
 
+  async importClaudeDesktopFromClaude(): Promise<number> {
+    return await invoke("import_claude_desktop_providers_from_claude");
+  },
+
+  async getClaudeDesktopStatus(): Promise<ClaudeDesktopStatus> {
+    return await invoke("get_claude_desktop_status");
+  },
+
+  async getClaudeDesktopDefaultRoutes(): Promise<ClaudeDesktopDefaultRoute[]> {
+    return await invoke("get_claude_desktop_default_routes");
+  },
+
   async updateTrayMenu(): Promise<boolean> {
     return await invoke("update_tray_menu");
   },

src/lib/api/skills.ts

@@ -4,6 +4,7 @@ import type { AppId } from "@/lib/api/types";
 
 export type AppType =
   | "claude"
+  | "claude-desktop"
   | "codex"
   | "gemini"
   | "opencode"
@@ -13,6 +14,7 @@ export type AppType =
 /** Skill 应用启用状态 */
 export interface SkillApps {
   claude: boolean;
+  "claude-desktop"?: boolean;
   codex: boolean;
   gemini: boolean;
   opencode: boolean;

src/lib/api/types.ts

@@ -1,6 +1,7 @@
 // 前端统一使用 AppId 作为应用标识（与后端命令参数 `app` 一致）
 export type AppId =
   | "claude"
+  | "claude-desktop"
   | "codex"
   | "gemini"
   | "opencode"