feat: bigger characters (16 sub-bodies), wider terminal viewport

- Entity: 16 sub-bodies (was 7), radius 0.7 (was 0.4), full humanoid
  shape: head, shoulders, torso, arms, hips, legs, feet
- Terminal: viewport up to 250x80 (was 120x50), uses full terminal size
- Camera: uses renderer viewport dimensions instead of hardcoded values
- Physics: constraint correction clamped to 0.5 cells max, 8 substeps
  (was 4), gravity 0.04 (was 0.08), collision pass after each constraint
  iteration to prevent tunneling with larger bodies
- Player: move_speed 0.3, jump_force 1.2 for bigger body
- Spawn: 6 cells above surface (was 4) for taller body

src/entity/player.rs

@@ -11,8 +11,8 @@ impl Player {
         let id = manager.spawn(EntityKind::Player);
         Self {
             entity_id: id,
-            move_speed: 0.15,
-            jump_force: 0.8,
+            move_speed: 0.3,
+            jump_force: 1.2,
         }
     }