[Bug]: TypeSpec VS Code Extension ignores VS Code Default Terminal

### Describe the bug

On startup TypeSpec VS Code extension throws an error:
```
[error] Launching server using command tsp failed. Error: spawn tsp ENOENT
[error] TypeSpec server executable was not found: 'tsp' is not found. Make sure either:
- TypeSpec is installed locally at the root of this workspace ("workspacePath") or in a parent directory.
- TypeSpec is installed globally with `npm install -g @typespec/compiler'.
- TypeSpec server path is configured with https://typespec.io/docs/introduction/editor/vscode/#configure.
[error] Error detail Launching server using command tsp failed. Error: spawn tsp ENOENT
```
However TypeSpec is installed globally and is accessible in PowerShell and set as VS Code's default terminal.
It is *not* accessible using the default system `cmd`

### Reproduction

Install/configure node/npm/tsc in a system terminal that isn't `cmd`, configure Visual Studio Code to use that terminal. The TypeSpec still extension fails to load.

### Checklist

- [x] Follow our [Code of Conduct](https://github.com/microsoft/typespec/blob/main/CODE_OF_CONDUCT.md)
- [x] Check that there isn't already an issue that request the same bug to avoid creating a duplicate.
- [x] Check that this is a concrete bug. For Q&A open a [GitHub Discussion](https://github.com/Microsoft/typespec/discussions).
- [x] The provided reproduction is a [minimal reproducible example](https://stackoverflow.com/help/minimal-reproducible-example) of the bug.