Revert "perf: enable GHA cache for base image layers in Docker builds"

This reverts commit a378c0f913.

.github/workflows/build-and-push.yaml

@@ -56,7 +56,5 @@ jobs:
           push: ${{ github.event_name != 'pull_request' }}
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
-          build-args: CACHE_BUST=${{ github.sha }}
+          no-cache: true
-          cache-from: type=gha
-          cache-to: type=gha,mode=max
           platforms: linux/amd64

.github/workflows/release-unified.yaml

@@ -96,9 +96,7 @@ jobs:
         with:
           context: .
           push: true
-          build-args: CACHE_BUST=${{ github.sha }}
+          no-cache: true
-          cache-from: type=gha
-          cache-to: type=gha,mode=max
           tags: |
             ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ steps.version.outputs.tag }}
             ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ steps.version.outputs.version }}

Dockerfile

@@ -56,13 +56,6 @@ exec /usr/bin/google-chrome-stable \\\n\
   "$@"\n' > /usr/local/bin/google-chrome && \
     chmod +x /usr/local/bin/google-chrome
 
-# --- Cache boundary ---
-# Everything above here is deterministic (apt packages, fixed base image) and
-# safe to serve from the Docker layer cache.  Everything below fetches "latest"
-# releases via curl, so a changing CACHE_BUST arg forces a rebuild from this
-# point onward while still reusing the expensive base-image / apt layers.
-ARG CACHE_BUST
-
 # Install Claude Code native binary (npm wrapper breaks remote control)
 RUN curl -fsSL https://claude.ai/install.sh | bash && \
     cp /root/.local/bin/claude /usr/local/bin/claude && \