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/render/terminal.rs

@@ -31,9 +31,9 @@ impl TerminalRenderer {
     }
 
     fn detect_size(&mut self) -> io::Result<()> {
-        let (w, h) = term_size().unwrap_or((80, 25));
-        self.width = (w as usize).min(120).max(40);
-        self.height = (h as usize).min(50).max(15);
+        let (w, h) = term_size().unwrap_or((120, 40));
+        self.width = (w as usize).min(250).max(60);
+        self.height = (h as usize).min(80).max(20);
         Ok(())
     }