feat(desktop): auto-update bundled skills on app launch

Skills installed via Paseo desktop never updated after first run, so
users were stuck on already-fixed skill content. On every launch, if
the paseo base skill is present in `~/.agents/skills/`, sync each
bundled skill (incl. `references/`) into agents, claude (via symlink/
junction), and codex — overwriting only files whose content differs.
Files on disk that are not in the bundle are left alone; deprecation
goes through tombstones (e.g. `paseo-orchestrate` redirects to
`paseo-epic`).

Also refreshes the bundled skill set: drops `paseo-chat`, adds
`paseo-advisor` and `paseo-epic`, and turns `paseo-orchestrate` into
a tombstone redirecting to `paseo-epic`.

Adds a desktop test job to CI on Ubuntu and Windows so the
junction/symlink path is exercised on both platforms.

packages/desktop/src/main.ts

@@ -43,6 +43,7 @@ import {
   createBeforeQuitHandler,
   stopDesktopManagedDaemonOnQuitIfNeeded,
 } from "./daemon/quit-lifecycle.js";
+import { autoUpdateSkillsIfInstalled } from "./integrations/integrations-manager.js";
 
 const DEV_SERVER_URL = process.env.EXPO_DEV_URL ?? "http://localhost:8081";
 const APP_SCHEME = "paseo";
@@ -392,6 +393,11 @@ async function bootstrap(): Promise<void> {
   registerDialogHandlers();
   registerNotificationHandlers();
   registerOpenerHandlers();
+
+  void autoUpdateSkillsIfInstalled().catch((error) => {
+    log.warn("[integrations] auto-update skills failed", error);
+  });
+
   await createMainWindow();
 
   app.on("activate", async () => {