Extension pane needs manual activation on Docker Desktop restart

[xenoscopic]

The extension SDK/API doesn't currently have a mechanism to trigger host-side executables before the extension pane is manually activated. This means that there's no way to start the host-side component of the extension (which provides the Mutagen Docker context and hosts Mutagen agent binaries) without the user clicking on the extension pane first.

This isn't a huge issue given that Docker Desktop isn't commonly restarted and the host-side component of the extension can outlive the pane once activated, but it is a rough edge and we should lobby for a solution.

If no solution is available in the near term, then we may need to look at a secondary installation step to integrate with launchd or the Windows registry or systemd to trigger automatic host-side startup.