ci: rewrite workflows for Gitea, use astral-uv runner, uv build only

Replaces the previous five JupyterLab-template workflows
(build / check-release / enforce-label / prep-release /
publish-release / update-integration-tests) with a single minimal
CI workflow tuned for a self-hosted Gitea runner.

What's in the new build.yml:
- Triggers: push to main, push of v* tag, pull_request
- runs-on: astral-uv (self-hosted runner with uv pre-installed;
  we skip the setup-uv step)
- Steps: checkout -> uv build -> upload-artifact
- uv build alone is enough because pyproject.toml's
  [tool.hatch.build.hooks.jupyter-builder] drives jlpm install
  and jlpm build:prod before wheel assembly, and uv caches the
  build environment between runs.

What's removed: all jupyter-server/jupyter_releaser steps and the
check-links / update-snapshots / test_isolated / integration-tests
jobs from the template — they depended on jupyterlab/maintainer-tools
and GitHub-specific secrets (GITHUB_TOKEN, APP_PRIVATE_KEY, NPM_TOKEN)
that don't apply to a Gitea deployment.

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

.github/workflows/build.yml

@@ -1,162 +1,32 @@
-name: Build
+name: CI
 
 on:
   push:
-    branches: main
+    branches:
+      - main
+    tags:
+        - 'v*'
   pull_request:
-    branches: '*'
-
-concurrency:
-  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
-  cancel-in-progress: true
 
 jobs:
-  build:
-    runs-on: ubuntu-latest
-
+  ci:
+    name: CI
+    # `astral-uv` is a self-hosted runner with uv pre-installed, so we can
+    # skip the setup-uv step entirely. pyproject.toml's
+    # [tool.hatch.build.hooks.jupyter-builder] handles jlpm install +
+    # jlpm build:prod before wheel assembly.
+    runs-on: astral-uv
     steps:
-    - name: Checkout
-      uses: actions/checkout@v4
+      - name: Checkout
+        uses: actions/checkout@v4
 
-    - name: Base Setup
-      uses: jupyterlab/maintainer-tools/.github/actions/base-setup@v1
+      - name: Build package
+        run: uv build
 
-    - name: Install dependencies
-      run: python -m pip install -U "jupyterlab>=4.0.0,<5"
-
-    - name: Lint the extension
-      run: |
-        set -eux
-        jlpm
-        jlpm run lint:check
-
-    - name: Test the extension
-      run: |
-        set -eux
-        jlpm run test
-
-    - name: Build the extension
-      run: |
-        set -eux
-        python -m pip install .[test]
-
-        pytest -vv -r ap --cov snapshot
-        jupyter server extension list
-        jupyter server extension list 2>&1 | grep -ie "snapshot.*OK"
-
-        jupyter labextension list
-        jupyter labextension list 2>&1 | grep -ie "snapshot.*OK"
-        python -m jupyterlab.browser_check
-
-    - name: Package the extension
-      run: |
-        set -eux
-
-        pip install build
-        python -m build
-        pip uninstall -y "snapshot" jupyterlab
-
-    - name: Upload extension packages
-      uses: actions/upload-artifact@v4
-      with:
-        name: extension-artifacts
-        path: dist/snapshot*
-        if-no-files-found: error
-
-  test_isolated:
-    needs: build
-    runs-on: ubuntu-latest
-
-    steps:
-    - name: Install Python
-      uses: actions/setup-python@v5
-      with:
-        python-version: '3.10'
-        architecture: 'x64'
-    - uses: actions/download-artifact@v4
-      with:
-        name: extension-artifacts
-    - name: Install and Test
-      run: |
-        set -eux
-        # Remove NodeJS, twice to take care of system and locally installed node versions.
-        sudo rm -rf $(which node)
-        sudo rm -rf $(which node)
-
-        pip install "jupyterlab>=4.0.0,<5" snapshot*.whl
-
-
-        jupyter server extension list
-        jupyter server extension list 2>&1 | grep -ie "snapshot.*OK"
-
-        jupyter labextension list
-        jupyter labextension list 2>&1 | grep -ie "snapshot.*OK"
-        python -m jupyterlab.browser_check --no-browser-test
-
-  integration-tests:
-    name: Integration tests
-    needs: build
-    runs-on: ubuntu-latest
-
-    env:
-      PLAYWRIGHT_BROWSERS_PATH: ${{ github.workspace }}/pw-browsers
-
-    steps:
-    - name: Checkout
-      uses: actions/checkout@v4
-
-    - name: Base Setup
-      uses: jupyterlab/maintainer-tools/.github/actions/base-setup@v1
-
-    - name: Download extension package
-      uses: actions/download-artifact@v4
-      with:
-        name: extension-artifacts
-
-    - name: Install the extension
-      run: |
-        set -eux
-        python -m pip install "jupyterlab>=4.0.0,<5" snapshot*.whl
-
-    - name: Install dependencies
-      working-directory: ui-tests
-      env:
-        YARN_ENABLE_IMMUTABLE_INSTALLS: 0
-        PLAYWRIGHT_SKIP_BROWSER_DOWNLOAD: 1
-      run: jlpm install
-
-    - name: Set up browser cache
-      uses: actions/cache@v4
-      with:
-        path: |
-          ${{ github.workspace }}/pw-browsers
-        key: ${{ runner.os }}-${{ hashFiles('ui-tests/yarn.lock') }}
-
-    - name: Install browser
-      run: |
-        set -eux
-        jlpm playwright install chromium --only-shell
-      working-directory: ui-tests
-
-    - name: Execute integration tests
-      working-directory: ui-tests
-      run: |
-        jlpm playwright test
-
-    - name: Upload Playwright Test report
-      if: always()
-      uses: actions/upload-artifact@v4
-      with:
-        name: snapshot-playwright-tests
-        path: |
-          ui-tests/test-results
-          ui-tests/playwright-report
-
-  check_links:
-    name: Check Links
-    runs-on: ubuntu-latest
-    timeout-minutes: 15
-    steps:
-      - uses: actions/checkout@v4
-      - uses: jupyterlab/maintainer-tools/.github/actions/base-setup@v1
-      - uses: jupyterlab/maintainer-tools/.github/actions/check-links@v1
+      - name: Upload wheel artifacts
+        if: success()
+        uses: actions/upload-artifact@v4
+        with:
+          name: snapshot-dist
+          path: dist/snapshot-*
+          if-no-files-found: error