Persist the FuncHost Wix framgment for troubleshooting

### Description

To assist with troubleshooting related to the MSI, we should persist the `-frag.wsx` file generated by `heat` when the MSI generation script is executed. This would enable us to verify component definitions and file manifests.

Locate the MSI generation script and the `heat` invocation that produces the `-frag.wsx` file. Make the generated fragment persist after the script runs, then verify that the saved file contains the component definitions and file manifest needed for troubleshooting.

Written by the indexing model from the issue text.