feat: cross-platform support — BSD adapters, clean gold bars, install docs (v8.4.0)

FreeBSD adapter scaffolds: pyusb detector, camcontrol SCSI (/dev/pass*),
sysctl+psutil sensors, geom hardware. Cleaned baked-in TRCC text from
10 gold bar PNGs — now rendered via QLabel. Added Windows/macOS/BSD
install sections to README. 37 new BSD tests (5207 total).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>