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.

.github/workflows/ci.yml

@@ -137,6 +137,26 @@ jobs:
           src/server/persisted-config.test.ts
           src/server/bootstrap-provider-availability.test.ts
 
+  desktop-tests:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, windows-latest]
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: "22"
+          cache: "npm"
+
+      - name: Install dependencies
+        run: npm install
+
+      - name: Run desktop tests
+        run: npm run test --workspace=@getpaseo/desktop
+
   app-tests:
     runs-on: ubuntu-latest
     steps: