Adds Microwaveprop.Canopy module that reads 1° × 1° uint8 per-degree
canopy-height tiles (mirrors SRTM .hgt naming/layout, 30 m resolution).
Returns 0 m for areas with no tile on disk so the lookup is safe to
thread through the existing path-clearance pipeline before any data
lands.
Wires canopy into:
- PathTerrain.obstacle_top: per-sample blocker = ground +
max(building_m, canopy_m), so the rover ranks paths through forests
as obstructed even when no buildings sit on the line
- CandidateDetail profile: each sample now carries canopy_m alongside
building_m
- Rover-detail SVG: green "trees" polygon stacked on terrain, under
the red building polygon
- Path calculator elevation chart: green Tree Canopy dataset between
terrain and buildings
Data prep (download Potapov 2019 / Lang 2022 GeoTIFF, slice to per-degree
uint8 tiles, drop in /data/canopy/) is a separate one-shot operation —
without tiles, lookups return 0 and the existing behavior is unchanged.
