World props: roads, bridges, rivers and coasts

Model and bake the 119 sprites of group shore of the world-props order (assets/requests/world-props/shore.md, brief assets/requests/world-props.md) on their own branch. Done when every sprite of the list is in assets/manifest.d/world_shore.toml, baked and reviewed on a gallery sheet.

Baked: all 119 (assets/manifest.d/world_shore.toml, scripts in tools/blender/models/world_shore/: roads, bridges, goods, boats, wrecks, beach, isles on shore_kit.py). Every script passes check_lattice(); frames, footprints and glows match the order. Conventions the bake should know: bridge and dock decks fill their tile (_x = the bridge or dock runs along x), parapets/railings stand on the north (_x) / west (_y) edge like fences (bridge_wood_post caps a railing run, as fence_*_post); dock_planks_end_x ends towards the east, _y towards the south; boats afloat have their waterline at z = 0.