Add CPU-only Docker image and fix release tag naming

- Add Dockerfile.cpu and compose.cpu.yaml for CPU-only deployments
- Use sentence-transformers[onnx] + CPU-only torch for ~4x smaller image
- Fix release script: separate git tags (engine-v*) from Docker tags (v*)
- Add CPU image to release build/push pipeline
- Update README with CPU deployment instructions

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

release-engine.sh

@@ -111,9 +111,11 @@ else
     echo "==> Engine version: $VERSION (no increment)"
 fi
 
-TAG="engine-v${VERSION}"
+GIT_TAG="engine-v${VERSION}"
+DOCKER_TAG="v${VERSION}"
 
-echo "    Tag:       $TAG"
+echo "    Git tag:   $GIT_TAG"
+echo "    Image tag: $DOCKER_TAG"
 echo "    Registry:  $IMAGE_BASE"
 echo "    Forge CLI: $FORGE"
 echo "    Dry run:   $DRY_RUN"
@@ -125,8 +127,8 @@ echo ""
 echo "==> Pre-flight checks"
 
 if [[ "$DRY_RUN" == false ]]; then
-    if git -C "$SCRIPT_DIR" rev-parse "$TAG" &>/dev/null; then
-        echo "Error: tag $TAG already exists"
+    if git -C "$SCRIPT_DIR" rev-parse "$GIT_TAG" &>/dev/null; then
+        echo "Error: tag $GIT_TAG already exists"
         exit 1
     fi
 fi
@@ -148,29 +150,32 @@ fi
 #──────────────────────────────────────────────────────────────────────
 echo "==> Building Docker engine images ($VERSION)"
 
-NVIDIA_IMAGE="${IMAGE_BASE}/engine:${TAG}-nvidia"
-ROCM_IMAGE="${IMAGE_BASE}/engine:${TAG}-rocm"
+NVIDIA_IMAGE="${IMAGE_BASE}/engine:${DOCKER_TAG}-nvidia"
+ROCM_IMAGE="${IMAGE_BASE}/engine:${DOCKER_TAG}-rocm"
+CPU_IMAGE="${IMAGE_BASE}/engine:${DOCKER_TAG}-cpu"
 NVIDIA_LATEST="${IMAGE_BASE}/engine:latest-nvidia"
 ROCM_LATEST="${IMAGE_BASE}/engine:latest-rocm"
+CPU_LATEST="${IMAGE_BASE}/engine:latest-cpu"
 
 run docker build -t "$NVIDIA_IMAGE" -t "$NVIDIA_LATEST" -f "$ENGINE_DIR/Dockerfile.nvidia" "$ENGINE_DIR"
 run docker build -t "$ROCM_IMAGE" -t "$ROCM_LATEST" -f "$ENGINE_DIR/Dockerfile.rocm" "$ENGINE_DIR"
+run docker build -t "$CPU_IMAGE" -t "$CPU_LATEST" -f "$ENGINE_DIR/Dockerfile.cpu" "$ENGINE_DIR"
 
 echo ""
 
 #──────────────────────────────────────────────────────────────────────
 # 4. Commit, tag, and push
 #──────────────────────────────────────────────────────────────────────
-echo "==> Committing and tagging $TAG"
+echo "==> Committing and tagging $GIT_TAG"
 
 if [[ "$INCREMENT" == true ]]; then
     run git -C "$SCRIPT_DIR" add "$VERSION_FILE"
     run git -C "$SCRIPT_DIR" commit -m "Bump engine version to $VERSION"
 fi
 
-run git -C "$SCRIPT_DIR" tag -a "$TAG" -m "Release $TAG"
+run git -C "$SCRIPT_DIR" tag -a "$GIT_TAG" -m "Release $GIT_TAG"
 run git -C "$SCRIPT_DIR" push origin HEAD
-run git -C "$SCRIPT_DIR" push origin "$TAG"
+run git -C "$SCRIPT_DIR" push origin "$GIT_TAG"
 
 echo ""
 
@@ -179,7 +184,7 @@ echo ""
 #──────────────────────────────────────────────────────────────────────
 echo "==> Creating release via $FORGE"
 
-RELEASE_TITLE="Engine $TAG"
+RELEASE_TITLE="Engine $GIT_TAG"
 RELEASE_NOTES="## Docker images
 
 \`\`\`bash
@@ -188,16 +193,19 @@ docker pull ${NVIDIA_IMAGE}
 
 # AMD GPU (ROCm)
 docker pull ${ROCM_IMAGE}
+
+# CPU only
+docker pull ${CPU_IMAGE}
 \`\`\`"
 
 if [[ "$FORGE" == "gh" ]]; then
-    run gh release create "$TAG" \
+    run gh release create "$GIT_TAG" \
         --title "$RELEASE_TITLE" \
         --notes "$RELEASE_NOTES"
 
 elif [[ "$FORGE" == "tea" ]]; then
     run tea release create \
-        --tag "$TAG" \
+        --tag "$GIT_TAG" \
         --title "$RELEASE_TITLE" \
         --note "$RELEASE_NOTES"
 fi
@@ -213,10 +221,13 @@ run docker push "$NVIDIA_IMAGE"
 run docker push "$NVIDIA_LATEST"
 run docker push "$ROCM_IMAGE"
 run docker push "$ROCM_LATEST"
+run docker push "$CPU_IMAGE"
+run docker push "$CPU_LATEST"
 
 echo ""
-echo "==> Release $TAG complete!"
+echo "==> Release $GIT_TAG complete!"
 echo ""
 echo "    Images:"
 echo "      $NVIDIA_IMAGE"
 echo "      $ROCM_IMAGE"
+echo "      $CPU_IMAGE"