The Windows installer's Install-Uv spawned the astral uv installer with a
hardcoded bare `powershell -ExecutionPolicy ByPass -c "irm .../uv | iex"`.
That name resolves only to Windows PowerShell, and only when its System32
directory is on PATH. Run under PowerShell 7+ (`pwsh`) — or any session where
`powershell` isn't on PATH — the spawn dies with "The term 'powershell' is not
recognized", and uv installation aborts (the installer then appears stuck).
Add Get-PowerShellHostExe, which prefers the absolute path of the host we're
already running in (PATH-independent), then falls back to powershell/pwsh via
Get-Command, then to the bare name. Install-Uv now invokes that resolved exe.
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