Port ue4-dev misc improvements to ue5-dev (Category 9: OpenDrive, Traffic, Python)

[youtalk]

Is your feature request related to a problem? Please describe.

The ue4-dev branch contains various improvements to OpenDrive parsing, traffic light/sign handling, and Python agents that have not been ported to ue5-dev. Part of the broader effort discussed in #9581.

Describe the solution you'd like

Port the following improvements as new implementations targeting ue5-dev:

• PR #0s feat(opendrive): lane marking and waypoint fixes — lane marking/tree generation fix (86fcfe5e8), waypoint next/previous with reversed connections (e41ffa03c), GetLaneCorners crash fix (4d4dd1d11), xml_node null pointer check (4ca87e818, 6cb77140c), OpenDriveActor custom path (58c870ae3)
• PR #0t feat(traffic): traffic light and sign improvements — floating sign fix (f856729ee), sign height adjustment refactor (e06993189), underground trigger box fix (c1ba7342c), OpenDRIVE signal trigger volume fix (2fed7136e), BoxComponent for sign height (363da3d78)
• PR #0u feat(python): agent improvements and InvertedAI — agent code modernization/typing (9a59963ca), BasicAgent set_destination improvement (4da0c7415), InvertedAI QoL (29af5dc89), InvertedAI scripts (b60034be6), obstacle detection empty list bug (694ad122a), carla.command import fix (aeeff9907)

Describe alternatives you've considered

Cherry-picking from ue4-dev was considered but rejected due to UE4→UE5 differences.

Additional context

This is Category 9 of the ue4-dev→ue5-dev porting effort. PRs #0s, #0t, #0u are independent and can be reviewed in parallel.