Add caching for Quartz setup in build workflow

Cache the Quartz clone and node_modules to speed up subsequent builds.
Only the content copy and build steps run on cache hit.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.forgejo/workflows/build-blumeops.yaml

@@ -40,13 +40,22 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
 
-      - name: Build Quartz site
+      # Cache Quartz installation (clone + node_modules)
+      # Key includes Quartz version; bump suffix to invalidate cache
+      - name: Restore Quartz cache
+        id: cache-quartz
+        uses: actions/cache@v4
+        with:
+          path: /tmp/quartz
+          key: quartz-v4.0.8-1
+
+      - name: Setup Quartz
+        if: steps.cache-quartz.outputs.cache-hit != 'true'
         run: |
-          VERSION="${{ inputs.version }}"
+          echo "Cache miss - setting up Quartz..."
           echo "Node version: $(node --version)"
           echo "NPM version: $(npm --version)"
 
-          echo "Setting up Quartz..."
           # Clone Quartz from local mirror
           git clone --depth 1 https://forge.ops.eblu.me/eblume/quartz.git /tmp/quartz
           cd /tmp/quartz
@@ -54,6 +63,13 @@ jobs:
           # Install dependencies
           npm ci
 
+          echo "Quartz setup complete"
+
+      - name: Build docs
+        run: |
+          VERSION="${{ inputs.version }}"
+          cd /tmp/quartz
+
           # Copy our configuration (lives in docs/ to keep repo root clean)
           cp "$GITHUB_WORKSPACE/docs/quartz.config.ts" .
           cp "$GITHUB_WORKSPACE/docs/quartz.layout.ts" .