refactor: manual mode from absolute setpoint to velocity control, remove auto-enable at motor init

Manual mode now receives angular velocity (degrees/s) via 0xA6 frame instead of
absolute angle reference. The firmware integrates velocity * dt into gimbal angle ref.
Motors are no longer auto-enabled at DMMotorInit — they stay disabled until a mode
switch out of DEBUG. Extract ROBOT_CMD_DELAY macro to replace magic number.
Fix "volity" typo → "velocity" and update docs/protocol comments accordingly.

modules/master_machine/master_machine.c

@@ -38,8 +38,8 @@ static void DecodeVision()
         if (calc_checksum(buf, VISION_MANUAL_LEN) != buf[VISION_MANUAL_LEN - 1])
             return;
         vision_data.zero_force = buf[1];
-        memcpy(&vision_data.yaw_ref,   buf + 2, 4);
-        memcpy(&vision_data.pitch_ref, buf + 6, 4);
+        memcpy(&vision_data.yaw_degree_velocity,   buf + 2, 4);
+        memcpy(&vision_data.pitch_degree_velocity, buf + 6, 4);
         vision_data.manual_updated = 1;
     }
     else if (sof == VISION_SOF_DEBUG && len == VISION_DEBUG_LEN)