Add UTF-8 BOM to PowerShell files with non-ASCII characters (#2195)

### ❔What, Why & How

PSScriptAnalyzer CI fails with:
```
Exception getting "Line": "The property 'StartLineNumber' cannot be found on this object."
```

Two files contain non-ASCII characters (box-drawing `├│└`, em-dash `—`)
without UTF-8 BOM. This triggers `PSUseBOMForUnicodeEncodedFile`, a
file-level rule that emits diagnostic records with no `Line` property —
crashing `ConvertTo-SARIF` when it accesses
`$this.Extent.StartLineNumber`.

- Added UTF-8 BOM to `Tests/CompileFromWorkspace.Test.ps1` and
`e2eTests/scenarios/WorkspaceCompilation/runtest.ps1`, consistent with
all other `.ps1`/`.psm1` files in the repo that contain non-ASCII
content.

### ✅ Checklist

- [ ] Add tests (E2E, unit tests)
- [ ] Update RELEASENOTES.md
- [ ] Update documentation (e.g. for new settings or scenarios)
- [ ] Add telemetry

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: mazhelez <43066499+mazhelez@users.noreply.github.com>