01 — op-1 tape undo / redo firmware

Adds supersaw, FM bell and granular synths, tape, clouds and reverb effects (also usable as master FX), a quad LFO, and euclid and dots sequencers. Also adds MIDI CC control, a scale mode and a storage bar on the COM screen. Lift, drop, slide, split and join can now be undone, undo history survives power off, and undo works on units with nearly full tape storage. Synths, effects and sequencers come from pcppcp's op1r.

Adds an UNDO / REDO popup modelled on the OP-1 field's, and snapshot naming on a tape-reel screen (up to 12 characters).

Tape undo / redo: hold TAPE and press ← or → to step up to 7 recordings back and forward again. Punch-ins, overdubs and loop recordings undo exactly, with the tape stopped or playing.

Fixed line in, mic and radio recording noise.

Added support for the latest revision displays and improved tape loop click reduction.

Added USB audio in and out, and improved external tempo sync stability. Tape now starts recording on an external play command when armed. Fixed several synth and sequencer crashes, and the SysEx identity reply now reports real version numbers.

Radio gain no longer affects mic gain on the rec screen, the vertical graphics tear in the screen center is gone, and octave shift works again in CTRL mode.