Add plugin zip build task and CI release artifact

- bin/build-zip.sh + `composer build`: stage runtime files only, generate a
  production (no-dev) optimized autoloader, and emit
  dist/<slug>-<version>.zip with a single top-level plugin folder, ready to
  upload via wp-admin. Tests, tooling configs, docs, and dev dependencies
  are excluded; version is read from the plugin header.
- CI `build` job: on push to main (post-merge), after lint/static-analysis/
  test/no-debug pass, runs the build and uploads the zip via
  actions/upload-artifact.
- Ignore build/ and dist/.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -101,3 +101,35 @@ jobs:
             echo "Debug code found in src/ — please remove before merging."
             exit 1
           fi
+
+  build:
+    name: Build Plugin Zip
+    runs-on: ubuntu-latest
+    # Only build a shippable artifact once changes land on main, and only
+    # after the quality gates pass.
+    needs: [lint, static-analysis, test, no-debug]
+    if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: '8.3'
+          tools: composer:v2
+
+      - name: Build plugin zip
+        run: composer build
+
+      - name: Read plugin version
+        id: meta
+        run: |
+          version="$(sed -nE 's/^[[:space:]]*\*?[[:space:]]*Version:[[:space:]]*([^[:space:]]+).*/\1/p' unsupervised-schedular.php | head -1)"
+          echo "version=${version}" >> "$GITHUB_OUTPUT"
+
+      - name: Upload artifact
+        uses: actions/upload-artifact@v3
+        with:
+          name: unsupervised-schedular-${{ steps.meta.outputs.version }}
+          path: dist/*.zip
+          if-no-files-found: error