Replace the Lemon/default font-switch with a single misc-fixed 6x9 font
(full Latin/Greek/Cyrillic coverage), generated via a new tools/bdf2gfx.py
BDF-to-GFX converter. Removes the keyboard's per-render font-switch
workarounds now that one font fits its cell cleanly.
DiagnosticsScreen becomes a circular tab carousel (Live / System / Font),
adding a firmware+device+radio info tab and a per-alphabet rendering test
card covering every keyboard language.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
