Add aggressive cache clearing before docker pull

The containerd content store isn't cleared by docker image rm alone.
Add docker builder prune and docker system prune to clear all caches.
Also add --platform linux/amd64 to be explicit about architecture.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

.github/workflows/docker_build.yml

@@ -268,12 +268,21 @@ jobs:
             # Use exact image tags passed from build jobs (no :latest fallback)
             echo "Using images: $EAGLE_IMAGE, $SHARDOK_IMAGE"
 
-            # Pull images with exact SHA tags
+            # Clear Docker's content store cache to avoid digest mismatch errors
+            # docker image rm isn't enough - need to clear buildkit and containerd cache
+            echo "Clearing Docker cache to avoid digest conflicts..."
+            docker builder prune -a -f 2>/dev/null || true
+            docker image rm "$EAGLE_IMAGE" "$SHARDOK_IMAGE" 2>/dev/null || true
+            # Nuclear option: clear all unused images/cache if digest issues persist
+            docker system prune -f 2>/dev/null || true
+
+            # Pull fresh images with exact SHA tags
+            # Use --platform to be explicit about architecture
             echo "Pulling Eagle image: $EAGLE_IMAGE"
-            docker pull "${EAGLE_IMAGE}" || { echo "ERROR: Failed to pull eagle image"; exit 1; }
+            docker pull --platform linux/amd64 "${EAGLE_IMAGE}" || { echo "ERROR: Failed to pull eagle image"; exit 1; }
 
             echo "Pulling Shardok image: $SHARDOK_IMAGE"
-            docker pull "${SHARDOK_IMAGE}" || { echo "ERROR: Failed to pull shardok image"; exit 1; }
+            docker pull --platform linux/amd64 "${SHARDOK_IMAGE}" || { echo "ERROR: Failed to pull shardok image"; exit 1; }
 
             # Also pull other compose images
             docker pull nginx:alpine || true