Changes all sleep screen display refreshes and boot screens from
FULL_REFRESH to HALF_REFRESH to match OEM firmware behavior. The stock
firmware uses a single-pass 0xD7 waveform for sleep screens, not the
multi-flash GC waveform (0xF7) that FULL_REFRESH triggers. For grayscale
mode, HALF_REFRESH is required because the gray nudge LUT is calibrated
against the pixel charge state left by the single-pass waveform; using
FULL_REFRESH causes blotchy noise in gray areas. Also adds X3 wb_gc
passive byte (the one-byte 0x54 to 0x00, matching stock's passive WB
table in the gc nudge bank): Every X3 grayscale render, reader AA,
covers, and the sleep-cover nudge, gets it.