fix: PATH variable expansion in ROCm worker Dockerfiles

Split ENV ROCM_HOME and ENV PATH into separate commands to fix variable
expansion issue. When ROCM_HOME and PATH were in the same ENV line,
${ROCM_HOME} expanded to empty string since it wasn't defined yet.

This was causing 'ray: command not found' in init containers.

dockerfiles/Dockerfile.ray-worker-rdna2

@@ -28,12 +28,12 @@ WORKDIR /app
 # Copy ROCm stack from vendor image (single COPY layer)
 COPY --from=rocm-source /opt/rocm /opt/rocm
 
-# ROCm environment variables
-ENV ROCM_HOME=/opt/rocm \
-    PATH="${ROCM_HOME}/bin:${ROCM_HOME}/llvm/bin:${PATH}" \
-    LD_LIBRARY_PATH="${ROCM_HOME}/lib:${ROCM_HOME}/lib64:${LD_LIBRARY_PATH}" \
-    HSA_PATH="${ROCM_HOME}/hsa" \
-    HIP_PATH="${ROCM_HOME}/hip" \
+# ROCm environment variables - split to ensure ROCM_HOME is set first
+ENV ROCM_HOME=/opt/rocm
+ENV PATH="/opt/rocm/bin:/opt/rocm/llvm/bin:/home/ray/anaconda3/bin:/home/ray/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin" \
+    LD_LIBRARY_PATH="/opt/rocm/lib:/opt/rocm/lib64" \
+    HSA_PATH="/opt/rocm/hsa" \
+    HIP_PATH="/opt/rocm/hip" \
     # RDNA 2 specific settings
     HIP_VISIBLE_DEVICES=0 \
     HSA_ENABLE_SDMA=0 \