fix: disable Docker layer cache in release builds

Release workflow was using GHA cache which served stale layers,
causing tools like gh CLI to be missing from tagged images despite
being in the Dockerfile. Use no-cache for release builds to ensure
every layer is built fresh. Regular CI builds keep the cache for speed.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.github/workflows/release-unified.yaml

@@ -96,11 +96,11 @@ jobs:
         with:
           context: .
           push: true
+          no-cache: true
           tags: |
             ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ steps.version.outputs.tag }}
             ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ steps.version.outputs.version }}
             ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:latest
-          cache-from: type=gha
           cache-to: type=gha,mode=max
           platforms: linux/amd64