Automate template creation, build, run, publish, and CI validation

## Objective

Add tests that install each template, generate projects with relevant options, restore, build, and publish them. Validate C# and VB, representative architectures and publish modes, expected file content, no unexpected diffs, and clean uninstall/update behavior.

## Completion guidance

- Keep the implementation focused on the objective while allowing the assignee to improve the approach based on research.
- Document important decisions, rejected alternatives, dependencies, and follow-up work.
- Add or update tests and documentation appropriate to the work.
- Verify locally and in CI where the task changes code or generated artifacts.

No files, tests, or CI entry points are named. Start by locating the template definitions and existing automation for installation, generation, restore, build, publish, and cleanup; done means coverage for C# and VB, representative architectures and publish modes, expected content, clean diffs, uninstall/update behavior, and local and CI verification.

Written by the indexing model from the issue text.