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/components/settings/AppVisibilitySettings.tsx

@@ -17,6 +17,11 @@ const APP_CONFIG: Array<{
   nameKey: string;
 }> = [
   { id: "claude", icon: "claude", nameKey: "apps.claude" },
+  {
+    id: "claude-desktop",
+    icon: "claude",
+    nameKey: "apps.claudeDesktop",
+  },
   { id: "codex", icon: "openai", nameKey: "apps.codex" },
   { id: "gemini", icon: "gemini", nameKey: "apps.gemini" },
   { id: "opencode", icon: "opencode", nameKey: "apps.opencode" },
@@ -32,6 +37,7 @@ export function AppVisibilitySettings({
 
   const visibleApps: VisibleApps = settings.visibleApps ?? {
     claude: true,
+    "claude-desktop": true,
     codex: true,
     gemini: true,
     opencode: true,
@@ -114,7 +120,7 @@ function AppButton({
       size="sm"
       variant={active ? "default" : "ghost"}
       className={cn(
-        "w-[90px] gap-1.5",
+        "min-w-[90px] w-auto gap-1.5 px-3",
         active
           ? "shadow-sm"
           : "text-muted-foreground hover:text-foreground hover:bg-muted",

src/components/settings/DirectorySettings.tsx

@@ -6,6 +6,8 @@ import { useTranslation } from "react-i18next";
 import type { AppId } from "@/lib/api";
 import type { ResolvedDirectories } from "@/hooks/useSettings";
 
+type DirectoryAppId = Exclude<AppId, "claude-desktop">;
+
 interface DirectorySettingsProps {
   appConfigDir?: string;
   resolvedDirs: ResolvedDirectories;
@@ -18,9 +20,9 @@ interface DirectorySettingsProps {
   opencodeDir?: string;
   openclawDir?: string;
   hermesDir?: string;
-  onDirectoryChange: (app: AppId, value?: string) => void;
-  onBrowseDirectory: (app: AppId) => Promise<void>;
-  onResetDirectory: (app: AppId) => Promise<void>;
+  onDirectoryChange: (app: DirectoryAppId, value?: string) => void;
+  onBrowseDirectory: (app: DirectoryAppId) => Promise<void>;
+  onResetDirectory: (app: DirectoryAppId) => Promise<void>;
 }
 
 export function DirectorySettings({