perf(desktop): reduce CPU/GPU overhead in Tauri shell

- SSH monitor: adaptive polling 2s→10s after stabilization, cheap TCP
  probe before expensive SSH subprocess check
- SSH setup: exponential backoff in wait_for_master_ready and
  wait_local_forward_ready (250ms→2s cap)
- Health checks: exponential backoff (100ms→1s / 250ms→2s) instead of
  flat intervals
- Startup recovery poll: cap at 15 retries instead of infinite
- Remove webview log target in release builds (eliminates IPC overhead)
- Set global NO_PROXY env var at startup for all loopback addresses
- Remove reqwest::blocking feature; use raw TCP for sidecar shutdown and
  SSH health checks
- Disable pinch-to-zoom on macOS via WKWebView.setAllowsMagnification
- Add WebView2 browser args on Windows (proxy bypass + disable unused
  UI features)
- Add Cargo release profile: thin LTO, codegen-units=1, strip
- Extract apply_platform_window_config for consistent window setup
- Add vibrancy toggle in Appearance settings (macOS desktop only) with
  solid background fallback when disabled

packages/ui/src/lib/desktop.ts

@@ -147,6 +147,8 @@ export type DesktopSettings = {
   skillCatalogs?: SkillCatalogConfig[];
   // Opt-in to send anonymous usage reports for update checks (default: true)
   reportUsage?: boolean;
+  // macOS window vibrancy effect (default: true)
+  desktopVibrancy?: boolean;
 };
 
 type TauriGlobal = {
@@ -637,3 +639,18 @@ export const clearDesktopCache = async (): Promise<boolean> => {
     return false;
   }
 };
+
+export const desktopSetVibrancy = async (enabled: boolean): Promise<boolean> => {
+  if (!isTauriShell()) {
+    return false;
+  }
+
+  try {
+    const tauri = (window as unknown as { __TAURI__?: TauriGlobal }).__TAURI__;
+    await tauri?.core?.invoke?.('desktop_set_vibrancy', { enabled });
+    return true;
+  } catch (error) {
+    console.warn('Failed to set vibrancy', error);
+    return false;
+  }
+};