Preserve signed target yaw in QuinticPathPlanner

[sylvesterkaczmarek]

Description

Fix target-prim yaw extraction and yaw-change comparison in QuinticPathPlanner.

When inputs:targetPrim is used, the node derives yaw from m.ExtractRotation().angle. That value is the rotation magnitude, not a signed Z-axis yaw, so a negative yaw can be flipped positive and rotation about another axis can be interpreted as yaw.

Extract the target transform quaternion instead and pass it through the node's existing quaternion-to-Euler conversion so the signed yaw is preserved.

The target-change threshold now also compares the wrapped yaw delta. This prevents physically close orientations on opposite sides of +pi/-pi from triggering a spurious replan.

Validation

• regression test verifies a target prim at -90° Z yields target yaw -pi/2
• regression test verifies +179° -> -179° is treated as a ~2° change, not ~358°
• test target is one metre from the robot to avoid a degenerate zero-length path
• production diff is four additions and two replacements