Type D contribution notes

[melw]

Hi! Independent Type D reverse-engineering, confirmed on D hardware, offered as notes toward native Type D in the single codebase. All addresses/patches are documentation; where a fix belongs in the hand-maintained base .rbn I've described it rather than patched it.

Highlights (full detail in docs/TYPE_D_CONTRIB.md):

• Boot freeze root cause + fix. The committed D base hangs at motor init.
• WB select_wb a1/a2 clobber fix (reload slots 0x2b7cc0/c8/cc).
• Quality patches — bitrate x2/x4, 3D-NR, FilmGrain (offsets + bytes)
• OSD notes — frame rate counter, ISO/Gain
• res/crop D geometry flagged as needing a confirming pass