Previously FOREST and ROCK tile types were always impassable, making 30 % of
forest floor and 50 % of rocky terrain permanently blocked even with no object
on them.
- Remove FOREST + ROCK from IMPASSABLE in types.ts
- Add RESOURCE_TERRAIN set (FOREST, ROCK) for tiles that need resource check
- WorldSystem: add resourceTiles Set<number> as O(1) spatial index
- initResourceTiles() builds index from state on create()
- addResourceTile() / removeResourceTile() keep it in sync at runtime
- isPassable() now: impassable tiles → false | RESOURCE_TERRAIN → check index | else → true
- GameScene: call addResourceTile() when SPAWN_RESOURCE fires (seedling matures)
- VillagerSystem: call removeResourceTile() after chop / mine completes
Side effect: trees fully enclosed by other trees are now reachable once an
adjacent tree is cleared; the hasAdjacentPassable() guard in pickJob still
correctly skips resources with zero passable neighbours.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
