Add type-specific transition-aware HetroD valid regions

[bob020416]

What changed

• centralize HetroD OSM subtype inference and polygon serialization
• emit schema 1.3 vehicle, cyclist, pedestrian core, crosswalk, and road layers
• retain a legacy pedestrian union for compatible map consumers
• use 0.75 m vehicle/cyclist/core and 1.5 m crosswalk margins
• describe the 1.5 m pedestrian road-corridor and 1.0 s transition-slack contract
• preserve significant polygon holes and exclude/report map-unsupported GT frames

Why

The old line-only map representation could not express type-specific valid regions, and a single pedestrian polygon could not represent legal sidewalk-road-sidewalk transitions. The new layers keep the map semantics explicit while allowing the evaluator to apply a small, auditable transition policy.

Validation

• converter modules compile successfully
• all six HetroD challenge maps converted successfully
• full rebuild completed for all 6,997 scenarios
• public package validation passed for 6,997 ScenarioNet files and 6,042 train/valid GT files
• all 955 public test inputs keep future states hidden
• representative perfect-GT replay passed across every validation location

Impact

Newly converted HetroD scenarios use schema 1.3 and policy type-specific-v3-pedestrian-transition-aware. The unrelated untracked scenarionet-wosac-gt/ directory is intentionally excluded.