Add QEMU support to CI CDK workflow for cross-platform Docker builds

Mirrors the enable-qemu input from cd-cdk.yaml. Required when CDK
stacks use PythonFunction or other Docker-bundled constructs targeting
arm64 Lambda on x86 CI runners.

.github/workflows/ci-typescript-cdk.yaml

@@ -23,6 +23,10 @@ on:
         description: "Run cdk synth"
         type: boolean
         default: true
+      enable-qemu:
+        description: "Enable QEMU for cross-platform Docker builds (arm64 on x86 runners)"
+        type: boolean
+        default: false
       run-sam-validate:
         description: "Run sam validate --lint (for Node.js SAM repos)"
         type: boolean
@@ -39,6 +43,9 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
+      - uses: docker/setup-qemu-action@v3
+        if: ${{ inputs.enable-qemu }}
+
       - uses: actions/setup-node@v4
         with:
           node-version: ${{ inputs.node-version }}