Update-UsageMonitor

Updates Usage Monitor for Claude to its latest GitHub release in one step, and shows
the release notes while the download is still running - the progress indicator is
drawn below the text instead of over it, so waiting time is reading time.

The downloaded build is verified against the SHA-256 digest GitHub publishes for it
and against its Authenticode signature; nothing is installed if verification fails.
The new file is staged beside the target so the final swap is atomic, and the previous
build is kept until that swap succeeds.

Steps:
 1. Reads the latest release of the given GitHub repository.
 2. Compares it with the version of the installed executable. If they match,
    asks whether to re-download and re-apply it anyway.
 3. Prints the release notes (changelog) of the new version.
 4. Closes every running instance of the executable.
 5. Downloads the matching asset for the current CPU architecture, verifies it
    (SHA-256 digest published by GitHub and/or Authenticode signature), then
    moves it over the installed copy.
 6. Restarts the main instance plus any additional instances defined by
    "<exe-name> - *.lnk" shortcuts sitting next to the executable.

The changelog stays readable while the download runs: the progress indicator is a
single line redrawn in place below the text, instead of Write-Progress, which
Windows PowerShell renders as a banner over the top of the console.