feat: Noita-style humanoid entities with per-part colors

Redesigned entity from solid 5x5 block to humanoid silhouette:

Shape (23 bodies, was 27):
     H H H        (head, 3 wide)
     H H H
   A T T T A      (shoulders + arms, 5 wide)
   A T T T A
     T T T        (torso, 3 wide)
     L   R        (legs, split with gap)
     L   R

Per-part colors (Noita-inspired):
- Player: head=bright yellow, torso=golden, arms=amber, legs=dark gold
- Goblin: head=bright green, torso=green, arms=olive, legs=dark green
- Corpse: desaturated browns

SubBody now has color: [u8; 4] field, set by build_humanoid.
All renderers (terminal, ascii, graphics) use b.color directly.
Fire effect: flickering orange overlay on burning entities.

half_w adjusted from 3.5 to 3.0, half_h from 2.5 to 3.5
(taller shape, narrower than old block).

109 tests, 0 failures

src/render/vulkan.rs

@@ -221,14 +221,8 @@ impl VulkanRenderer {
                     };
                     let fg = if e.on_fire {
                         [255, 160, 40, 255]
-                    } else if !e.alive {
-                        [100, 60, 60, 255]
                     } else {
-                        match e.kind {
-                            EntityKind::Player => [255, 255, 100, 255],
-                            EntityKind::Goblin => [100, 220, 100, 255],
-                            _ => [180, 50, 50, 255],
-                        }
+                        b.color
                     };
                     entity_map.insert((sx, sy), (ch, fg));
                 }