CI: Windows build + release on yuuka-windows

tool/package_windows.ps1 builds watch-together-<ver>-windows-x64.zip
(same layout as the Linux tarball, libmpv bundled, update.bat and
watch-together-server.exe). The release workflow gets a windows job;
ci runs the updater tests on Windows. Publishing moves to
tool/release_publish.dart (dart: only, no python/bash on Windows), which
tolerates both jobs racing to create the release and replaces an asset
on re-runs. release.sh writes both asset URLs into the manifest.
Windows jobs check out with plain git (the host's cached
actions/checkout clone was corrupt).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -36,3 +36,24 @@ jobs:
         working-directory: packages/server
       - run: build/watch-together-server --help
         working-directory: packages/server
+
+  # The updater's Windows apply path (running exe parked as .old) only
+  # means something on real NTFS. Runner notes: see release.yml.
+  updater-windows:
+    runs-on: windows-latest
+    steps:
+      - name: Checkout
+        shell: powershell
+        run: |
+          git init -q .
+          git remote add origin "$env:GITHUB_SERVER_URL/$env:GITHUB_REPOSITORY.git"
+          git fetch -q origin "$env:GITHUB_SHA"
+          if ($LASTEXITCODE) { exit 1 }
+          git checkout -q --force FETCH_HEAD
+      - name: Setup Flutter
+        shell: powershell
+        run: powershell -NoProfile -ExecutionPolicy Bypass -File tool/setup_flutter_windows.ps1
+      - name: Updater tests
+        shell: powershell
+        working-directory: apps/desktop
+        run: flutter test test/updater_test.dart