docs: add unit and range documentation to message fields (#107)

* docs: add unit and range documentation to message fields

Add inline comments to clarify units and valid ranges for:
- PedalsCommand.msg: throttle/brake range (0.0-1.0)
- SteeringCommand.msg: steering_tire_angle [rad], velocity [rad/s]
- VelocityFactor.msg: distance [m], field descriptions

Related to #106

* docs: clarify behavior field accepts user-defined values

* Update autoware_adapi_v1_msgs/planning/msg/VelocityFactor.msg

Author: youtalk

autoware_adapi_v1_msgs/manual/msg/PedalsCommand.msg

@@ -1,3 +1,5 @@
 builtin_interfaces/Time stamp
+# Throttle pedal position. Range: 0.0 to 1.0 (normalized)
 float32 throttle
+# Brake pedal position. Range: 0.0 to 1.0 (normalized)
 float32 brake

autoware_adapi_v1_msgs/manual/msg/SteeringCommand.msg

@@ -1,3 +1,5 @@
 builtin_interfaces/Time stamp
+# Steering tire angle [rad]. Positive: left, Negative: right
 float32 steering_tire_angle
+# Steering tire angular velocity [rad/s]
 float32 steering_tire_velocity

autoware_adapi_v1_msgs/planning/msg/VelocityFactor.msg

@@ -2,14 +2,21 @@
 uint16 UNKNOWN = 0
 
 # constants for status
-uint16 APPROACHING = 1
-uint16 STOPPED = 2
+uint16 APPROACHING = 1  # Vehicle is approaching the factor
+uint16 STOPPED = 2      # Vehicle has stopped due to the factor
 
-# variables
+# fields
+# Pose of the velocity factor in VelocityFactorArray.header.frame_id
 geometry_msgs/Pose pose
+# Distance to the velocity factor [m]
 float32 distance
+# Current status (use status constants above)
 uint16 status
+# Behavior type (see PlanningBehavior.msg for typical values, any name is available for user extensions)
 string behavior
+# Planning sequence identifier
 string sequence
+# Detailed description of the factor
 string detail
+# Cooperation status (optional, max 1 element)
 autoware_adapi_v1_msgs/CooperationStatus[<=1] cooperation