Add validated HetroD type-specific valid regions

[bob020416]

What changed

• add a centralized HetroD valid-region policy and OSM subtype inference rules
• preserve lanelet polygons and serialize per-type valid regions into ScenarioNet metadata
• standardize boundary margins at vehicle 0.75 m, cyclist 0.75 m, and pedestrian 2.0 m
• preserve polygon holes larger than 5 m² while filling small geometry artifacts
• add visualization and full validation-GT audit tools

Why

The previous conversion exposed map lines but did not provide explicit agent-type valid regions. Direct OSM semantics also left systematic boundary misses, particularly for pedestrians. The selected type-specific margins preserve semantic differences while achieving at least 90% pedestrian GT center coverage in every validation location represented by GT.

Validation

• Python compilation passed for all four changed scripts
• converter-level smoke test passed on all six HetroD OSM maps
• full audit passed over 955 validation scenarios
• OSM-to-ScenarioNet alignment: mean RMSE 0.000042 m, maximum point error 0.000222 m
• pedestrian GT center coverage: loc0 99.52%, loc1 94.18%, loc3 94.39%, loc4 90.36%, loc5 95.52%; loc2 has no validation scenarios

Impact

Newly converted scenarios use schema 1.2 and policy type-specific-v2-buffered. Existing unrelated scenarionet-wosac-gt/ working-tree files are intentionally excluded.