AIDemon2 2.1.0

Added

• Releases now ship a portable ZIP, and that is the artifact to use. Unpack it and run
  AIDemon2.exe — no installer, no .NET runtime needed, nothing written outside
  %LOCALAPPDATA%\AIDemon2\. About 42 MB, self-contained.

Fixed

• Previous releases could not be installed at all. The MSIX shipped unsigned, and Windows
  refuses a package with no trust chain outright — not a warning to click through, but a flat
  refusal. CONTRIBUTING.md compounded this by claiming the unsigned package was "installable
  via the bundled Add-AppDevPackage.ps1", which was wrong on both counts: that script is not
  in the release, and it would not have helped. The MSIX is still published for the day a
  certificate is available, and both files now say plainly which one to use.