feat: Optimize Docker PR builds for speed

- Only trigger PR builds when Docker-related files change
- Skip Docker Hub login/push for PR builds (build-only validation)
- Use single platform (amd64) for PR builds vs multi-platform for releases
- Skip claudecode build entirely for PRs
- Keep aggressive GitHub Actions caching for faster rebuilds
- Add path filtering to prevent unnecessary Docker builds

.github/workflows/docker-publish.yml

@@ -11,6 +11,12 @@ on:
     branches:
       - main
       - master
+    paths:
+      - 'Dockerfile*'
+      - 'package*.json'
+      - '.github/workflows/docker-publish.yml'
+      - 'src/**'
+      - 'scripts/**'
 
 env:
   DOCKER_HUB_USERNAME: cheffromspace
@@ -52,8 +58,8 @@ jobs:
             type=semver,pattern={{major}}
             # Latest tag for semantic version tags
             type=raw,value=latest,enable=${{ startsWith(github.ref, 'refs/tags/v') }}
-            # SHA for branch builds only
-            type=sha,prefix={{branch}}-,enable=${{ github.event_name == 'push' && github.ref_type == 'branch' }}
+            # SHA for branch builds (push only)
+            type=sha,prefix={{branch}}-,enable=${{ github.event_name != 'pull_request' }}
             # For PR builds, use pr-NUMBER
             type=ref,event=pr
 
@@ -61,7 +67,7 @@ jobs:
         uses: docker/build-push-action@v5
         with:
           context: .
-          platforms: linux/amd64,linux/arm64
+          platforms: ${{ github.event_name == 'pull_request' && 'linux/amd64' || 'linux/amd64,linux/arm64' }}
           push: ${{ github.event_name != 'pull_request' }}
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}