Add enable-qemu input to CI workflow for arm64 cdk synth bundling

.github/workflows/ci-python-sam.yaml

@@ -35,6 +35,10 @@ on:
         description: "Node.js version for CDK CLI"
         type: string
         default: "24"
+      enable-qemu:
+        description: "Enable QEMU so cdk synth can bundle arm64 Lambda assets on x86 runners"
+        type: boolean
+        default: false
       run-conventions-check:
         description: "Run lightweight conventions audit"
         type: boolean
@@ -80,6 +84,10 @@ jobs:
         with:
           node-version: ${{ inputs.node-version }}
 
+      - name: Set up QEMU
+        if: ${{ inputs.run-cdk-synth && inputs.enable-qemu }}
+        uses: docker/setup-qemu-action@v3
+
       - name: CDK synth
         if: ${{ inputs.run-cdk-synth }}
         working-directory: ${{ inputs.cdk-dir }}