feat: detailed characters + Noita-style mouse aiming

Character detail:
- Player: 68 body parts (was 42) — eyes, hair, cape, hat, gloves
- Goblin: 56 body parts (was 39) — red eyes, pointed ears, teeth, skin tones
- New body labels: eye, hair, cape, tooth, ear
- Updated preview_ascii label map for new part types

Mouse aiming (Noita-style):
- Track mouse position via CursorMoved events
- Track left-click via MouseInput events
- Left-click shoots projectile toward mouse cursor direction
- Player faces left/right based on mouse X relative to player screen X
- Keyboard shoot (hjkl) still works as fallback
- Player.facing_right field added
- WindowInput: mouse_x, mouse_y, mouse_left, shoot_mouse fields
- on_mouse_move(), on_mouse_button() handlers
- clear_keys() also clears mouse state on focus loss

All 171 tests + 14 scenarios pass.

AGENTS.md

@@ -45,13 +45,15 @@ Terminal (`--mode terminal`):
 GPU (`--mode ascii` / `--mode graphics`):
 - `a` / `d` or `←` / `→` — move
 - `w` / `↑` / `space` — jump
-- `h` / `j` / `k` / `l` — shoot left / down / up / right
+- `h` / `j` / `k` / `l` — shoot left / down / up / right (keyboard fallback)
+- **Left-click** — shoot toward mouse cursor (Noita-style aiming)
+- **Mouse position** — player faces mouse direction (left/right)
 - `f` — toggle fireball mode
 - `>` / `.` — descend when standing on stairs
 - `e` — use/equip first inventory item
 - `r` — drop first inventory item
 - `1`–`0` / `x` — paint material brush
-- `y` / `u` / `i` / `o` — move camera
+- `y` / `u` / `i` / `o` — move camera offset
 - `q` / `esc` — quit
 
 ## Shaders