F2 Control screen Manual mode now has a row of step-size buttons
(0.1°, 0.5°, 1°, 5°, 10°) that scale arrow key nudges, plus
AZ/EL velocity inputs with Apply button for runtime motor speed
tuning via firmware mv/ma commands.
Bridge: set_max_velocity(), set_max_acceleration() write methods.
Demo: mutable dynamics + console mv/ma write handling.
Tests: 8 Textual pilot tests covering button toggle, nudge math,
velocity population, and apply round-trip.
