slab/menuband: octave reads "4" with hint label, synth-start log
- Octave label shows the absolute pitch number (4 by default, since the
menubar piano starts at C4) instead of the +N/-N relative shift. A
tiny "octave" hint label sits to the right so the number reads as
scientific pitch notation at a glance.
- One-line NSLog after engine.start so it's visible in the launchd
log whether the GS DLS bank actually loaded (status=0 == noErr).
- DMG cache-bust → ?v=59b8d6b.