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.h

@@ -16,9 +16,9 @@
  *   error_x/y: float, 归一化误差, 视觉PID外环反馈值
  *
  * ---- 手动控制数据帧 0xA6 (11 字节) ----
- *   [SOF:0xA6][zero_force:1][yaw_ref:4][pitch_ref:4][checksum:1]
- *   zero_force: 0=正常角度控制, 1=零力/保持当前位置
- *   yaw_ref/pitch_ref: float, 角度参考值 (degrees)
+ *   [SOF:0xA6][zero_force:1][yaw_velocity:4][pitch_velocity:4][checksum:1]
+ *   zero_force: 0=正常速度控制, 1=零力/保持当前位置
+ *   yaw_velocity/pitch_velocity: float, 角速度 (degrees/s)
  *
  * ---- 命令帧 0xA7 (3 字节) ----
  *   [SOF:0xA7][cmd:1][checksum:1]
@@ -68,8 +68,8 @@ typedef struct
 
     /* 手动模式数据 */
     uint8_t zero_force;
-    float yaw_ref;
-    float pitch_ref;
+    float yaw_degree_velocity;
+    float pitch_degree_velocity;
     uint8_t manual_updated; // 收到新的手动数据帧标志
 
     /* 调试模式数据 */