feat: Configure Nav2 navigation stack conservative speeds (Issue #475)

- Update max_vel_x to 0.3 m/s (conservative for FC + hoverboard ESC)
- Update max_vel_theta to 0.5 rad/s (conservative for FC + hoverboard ESC)
- Set robot_radius to 0.22 m for 0.4m x 0.4m footprint
- Configure velocity smoother with conservative limits
- Both DWB local planner and velocity smoother updated for consistency
- RPLIDAR (/scan) + depth_to_laserscan (/depth_scan) costmap layers enabled
- NavFn global planner, DWB local planner configured

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

jetson/ros2_ws/src/saltybot_bringup/config/nav2_params.yaml

@@ -1,10 +1,10 @@
 # Nav2 parameters — SaltyBot (Jetson Orin Nano Super / ROS2 Humble)
 #
 # Robot: differential-drive self-balancing two-wheeler
-#   robot_radius:   0.15 m  (~0.2m with margin)
-#   footprint:      0.4 x 0.4 m (x 2m for buffer)
-#   max_vel_x:      1.0  m/s
-#   max_vel_theta:  1.5  rad/s
+#   robot_radius:   0.22 m (0.4m x 0.4m footprint)
+#   footprint:      0.4 x 0.4 m
+#   max_vel_x:      0.3  m/s (conservative for FC + hoverboard ESC, Issue #475)
+#   max_vel_theta:  0.5  rad/s (conservative for FC + hoverboard ESC, Issue #475)
 #
 # Localization: RTAB-Map (publishes /map + map→odom TF + /rtabmap/odom)
 #   → No AMCL, no map_server needed.
@@ -120,14 +120,14 @@ controller_server:
     FollowPath:
       plugin: "dwb_core::DWBLocalPlanner"
       debug_trajectory_details: false
-      # Velocity limits
-      min_vel_x: -0.25          # allow limited reverse
+      # Velocity limits (conservative for FC + hoverboard ESC, Issue #475)
+      min_vel_x: -0.15          # allow limited reverse (half of max forward)
       min_vel_y: 0.0
-      max_vel_x: 1.0
+      max_vel_x: 0.3            # conservative: 0.3 m/s linear
       max_vel_y: 0.0
-      max_vel_theta: 1.5
+      max_vel_theta: 0.5         # conservative: 0.5 rad/s angular
       min_speed_xy: 0.0
-      max_speed_xy: 1.0
+      max_speed_xy: 0.3          # match max_vel_x
       min_speed_theta: 0.0
       # Acceleration limits (differential drive)
       acc_lim_x: 2.5
@@ -243,14 +243,15 @@ waypoint_follower:
       waypoint_pause_duration: 200
 
 # ── Velocity Smoother ────────────────────────────────────────────────────────
+# Conservative speeds for FC + hoverboard ESC (Issue #475)
 velocity_smoother:
   ros__parameters:
     use_sim_time: false
     smoothing_frequency: 20.0
     scale_velocities: false
     feedback: "OPEN_LOOP"
-    max_velocity: [1.0, 0.0, 1.5]
-    min_velocity: [-0.25, 0.0, -1.5]
+    max_velocity: [0.3, 0.0, 0.5]           # conservative: 0.3 m/s linear, 0.5 rad/s angular
+    min_velocity: [-0.15, 0.0, -0.5]
     max_accel: [2.5, 0.0, 3.2]
     max_decel: [-2.5, 0.0, -3.2]
     odom_topic: /rtabmap/odom
@@ -271,7 +272,7 @@ local_costmap:
       width: 3
       height: 3
       resolution: 0.05
-      robot_radius: 0.15
+      robot_radius: 0.22
       # Footprint: [x, y] in base_link frame, in counterclockwise order
       # Robot footprint ~0.4m x 0.4m, with 2m lookahead buffer for controller stability
       footprint: "[[-0.2, -0.2], [-0.2, 0.2], [0.2, 0.2], [0.2, -0.2]]"
@@ -342,7 +343,7 @@ global_costmap:
       publish_frequency: 1.0
       global_frame: map
       robot_base_frame: base_link
-      robot_radius: 0.15
+      robot_radius: 0.22
       # Footprint: [x, y] in base_link frame, in counterclockwise order
       footprint: "[[-0.2, -0.2], [-0.2, 0.2], [0.2, 0.2], [0.2, -0.2]]"
       resolution: 0.05