Add loading screen, fix tree/foliage collision, jump buffering, and fence rotation

- Loading screen stays visible until all terrain tiles finish streaming;
  character spawns only after terrain is loaded and Z-snapped to ground
- Reduce tree trunk collision bounds (5% of canopy, capped at 5.0) and
  make all small/medium trees, bushes, lily pads, and foliage walkthrough
- Add jump input buffering (150ms) and coyote time (100ms) for responsive jumps
- Fix fence orientation by adding +180° heading rotation
- Increase terrain load radius from 1 to 2 (5x5 tile grid)
- Add hearthstone callback for single-player camera reset

include/rendering/m2_renderer.hpp

@@ -47,6 +47,7 @@ struct M2ModelGPU {
     bool collisionPlanter = false;
     bool collisionSmallSolidProp = false;
     bool collisionNarrowVerticalProp = false;
+    bool collisionTreeTrunk = false;
     bool collisionNoBlock = false;
     bool collisionStatue = false;