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/providers/forms/ProviderForm.tsx

@@ -59,6 +59,7 @@ import { Label } from "@/components/ui/label";
 import { ProviderPresetSelector } from "./ProviderPresetSelector";
 import { BasicFormFields } from "./BasicFormFields";
 import { ClaudeFormFields } from "./ClaudeFormFields";
+import { ClaudeDesktopProviderForm } from "./ClaudeDesktopProviderForm";
 import { CodexFormFields } from "./CodexFormFields";
 import { GeminiFormFields } from "./GeminiFormFields";
 import { OmoFormFields } from "./OmoFormFields";
@@ -115,7 +116,7 @@ type PresetEntry = {
     | HermesProviderPreset;
 };
 
-interface ProviderFormProps {
+export interface ProviderFormProps {
   appId: AppId;
   providerId?: string;
   submitLabel: string;
@@ -137,7 +138,15 @@ interface ProviderFormProps {
   showButtons?: boolean;
 }
 
-export function ProviderForm({
+export function ProviderForm(props: ProviderFormProps) {
+  if (props.appId === "claude-desktop") {
+    return <ClaudeDesktopProviderForm {...props} />;
+  }
+
+  return <ProviderFormFull {...props} />;
+}
+
+function ProviderFormFull({
   appId,
   providerId,
   submitLabel,
@@ -149,6 +158,10 @@ export function ProviderForm({
   initialData,
   showButtons = true,
 }: ProviderFormProps) {
+  if (appId === "claude-desktop") {
+    throw new Error("ProviderFormFull should not receive claude-desktop");
+  }
+
   const { t } = useTranslation();
   const isEditMode = Boolean(initialData);
   const queryClient = useQueryClient();
@@ -1165,6 +1178,7 @@ export function ProviderForm({
               ? useGeminiCommonConfigFlag
               : undefined,
       endpointAutoSelect,
+      claudeDesktopMode: undefined,
       // 保存 providerType（用于识别 Copilot / Codex OAuth 等特殊供应商）
       providerType,
       authBinding: isCopilotProvider
@@ -1797,6 +1811,7 @@ export function ProviderForm({
               }
               autoSelect={endpointAutoSelect}
               onAutoSelectChange={setEndpointAutoSelect}
+              showEndpointTools
               shouldShowModelSelector={category !== "official"}
               claudeModel={claudeModel}
               defaultHaikuModel={defaultHaikuModel}