Align start waypoint with lane exit waypoint for consistency

[kjchee]

Bug fix

Fixed bug

This PR is not a bug fix but a preventive measure to ensure the planner always starts with a consistent lane-waypoint combination (start's waypoint = lane's exit waypoint).

Related context: Grey’s comment

Fix applied

The validation is applied upstream within SearchNodePtr make_start_node(), which constructs the planner’s initial search node. If a start condition specifies both a lane and waypoint that are inconsistent, the function automatically corrects the start’s waypoint to match the exit waypoint of the specified lane.

This guarantees that all downstream planner logic (e.g., the start will be passed down & used in other functions like make_start_approach_trajectories() or used to construct the current & next SearchNode) operates on a consistent and valid start configuration.

GenAI Use

We follow OSRA's policy on GenAI tools

• I used a GenAI tool in this PR.
• I did not use GenAI