Remove the GitHub Actions workflow; Gitea is the CI host

The team hosts on Gitea, so .github/workflows/ci.yml is dead weight. The Gitea
workflow (.gitea/workflows/ci.yml) is the single source of CI: lint + headless
tests on push/PR, plus the daily safety-net run.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017KoYBYQgRyY1zDHXMsXY3V

.github/workflows/ci.yml

@@ -1,52 +0,0 @@
-name: CI
-
-on:
-  push:
-  pull_request:
-
-jobs:
-  test:
-    name: Lint & headless tests
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v4
-
-      # Mirror the local toolchain (godot --version → 4.7.beta). If this exact tag is not published,
-      # pin it to the 4.7 beta the team actually runs; setup-godot maps this to a Godot release tag.
-      - name: Install Godot 4.7
-        uses: chickensoft-games/setup-godot@v2
-        with:
-          version: 4.7.0-beta
-          use-dotnet: false
-          include-templates: false
-
-      - name: Set up Python
-        uses: actions/setup-python@v5
-        with:
-          python-version: "3.12"
-
-      - name: Install gdlint (gdtoolkit)
-        run: pip install "gdtoolkit==4.*"
-
-      # First run imports assets and builds the .godot cache (gitignored), so the headless tests can
-      # actually load the .glb/.png resources they instance. Import can exit non-zero on warnings.
-      - name: Import resources
-        run: godot --headless --import
-        continue-on-error: true
-
-      - name: gdlint
-        run: gdlint actors systems ui props levels tests
-
-      - name: Headless tests
-        env:
-          GODOT: godot
-        run: bash run_tests.sh --no-gameplay
-
-      - name: Upload test output on failure
-        if: failure()
-        uses: actions/upload-artifact@v4
-        with:
-          name: test-output
-          path: tests/output/
-          if-no-files-found: ignore