feat: cel-shaded look & feel overhaul — real audio, comic UI, themed VFX

Audio (all CC0 — Kenney packs + OpenGameArt, see assets/sounds/SOURCES.md):
- Replace every procedural synth WAV with forged sounds (ffmpeg pitch/layer
  mixes): distinct fire sounds per weapon with 2-3 variations, explosions,
  footsteps x5, land/jump/dash/vault, knife swing, hit/kill confirms,
  bullet impacts, reload, flight loops, UI hover/click/confirm/error,
  match jingles, menu music
- AudioManager.stream_for(): AudioStreamRandomizer per sound id — every
  weapon now gets variation + pitch randomization on each shot
- Explosions and bullet impacts play positional audio; landing has its own
  sound instead of a pitched footstep; ambient wind bed on every map

Visuals:
- ExplosionVFX: shared cel-shaded burst (white-hot stepped core, ink
  shockwave ring, star spikes, flat smoke puffs) replaces the orange
  sphere in both local and remote-replay paths
- Comic star muzzle flashes on all weapons; unified cel tracer bolts with
  ink outlines across hitscan/shotgun/remote paths
- Impact decals: hard-stepped ink-splat gradients instead of soft airbrush
- Toon shading on first-person view models + arms, third-person weapons,
  and the procedural humanoid fallback (no hull outlines on FBX weapons —
  their hard normals tear the inverted hull)
- Fix: giant soft "blob" highlight on floors — toon rim/specular disabled
  on level-geometry materials (pre-existing artifact since the cel commit)
- Fix: own third-person weapon rendered into the first-person camera
  (shadows-only now covers first_person_mode)

UI:
- UITheme: comic theme on the root window — Bangers display font (OFL),
  paper panels with thick ink borders + hard drop shadows, papaya accent,
  themed buttons/inputs/popups; hover/click sounds on all menu buttons
- Main menu: tilted comic wordmark, sunset toon diorama, looping menu music
- Match HUD: themed scoreboard/killfeed/kill counter

Viewports:
- 4x MSAA project-wide + viewmodel/diorama viewports (crisp ink lines)
- Viewmodel camera near plane 0.01; third-person camera FOV syncs settings
- debug/visual_capture.gd: dev tool to screenshot menu + level for review

Verified: 11/11 movement tests, spawn smoke test 0 failures, before/after
screenshot comparison of menu and level.

Co-Authored-By: Claude Fable 5 <[email protected]>

weapons/base_hitscan_weapon.gd

@@ -111,6 +111,7 @@ func _fire() -> void:
 
 func _play_muzzle_flash() -> void:
 	if muzzle_flash:
+		ExplosionVFX.muzzle_flash(muzzle_flash.get_parent(), muzzle_flash.position)
 		muzzle_flash.light_energy = 8.0
 		var tween = create_tween()
 		tween.tween_property(muzzle_flash, "light_energy", 0.0, 0.05)
@@ -175,33 +176,6 @@ func _shoot_hitscan() -> void:
 		player.server_play_fire_effects.rpc_id(1, origin, final_target, name, true)
 
 func _spawn_tracer(_origin: Vector3, final_target: Vector3) -> void:
-	# Spawn cosmetic tracer
-	var tracer = Node3D.new()
-	tracer.set_script(load("res://weapons/hitscan_tracer.gd"))
-	
-	var t_mesh_inst = MeshInstance3D.new()
-	var t_mesh = CapsuleMesh.new()
-	t_mesh.radius = 0.02
-	t_mesh.height = 1.0
-	var t_mat = StandardMaterial3D.new()
-	t_mat.albedo_color = Color(1.0, 0.8, 0.2) # Yellow-orange tracer
-	t_mat.emission_enabled = true
-	t_mat.emission = Color(2.0, 1.5, 0.5)
-	t_mesh.material = t_mat
-	
-	t_mesh_inst.mesh = t_mesh
-	t_mesh_inst.rotation.x = deg_to_rad(90) # Orient capsule along Z axis
-	t_mesh_inst.position = Vector3(0, 0, -0.5) # Shift it half a meter forward so the tail is at the origin
-	tracer.add_child(t_mesh_inst)
-	
-	tracer.target_position = final_target
-	var visual_origin = muzzle_flash.global_position if muzzle_flash else global_position # Spawn from the barrel tip
-	
-	if visual_origin.distance_squared_to(final_target) > 0.1:
-		get_tree().current_scene.add_child(tracer)
-		tracer.global_position = visual_origin
-		
-		var up_vec = Vector3.UP
-		if abs((final_target - visual_origin).normalized().dot(up_vec)) > 0.99:
-			up_vec = Vector3.RIGHT
-		tracer.look_at(final_target, up_vec)
+	# Cel-styled cosmetic tracer from the barrel tip
+	var visual_origin = muzzle_flash.global_position if muzzle_flash else global_position
+	HitscanTracer.spawn_bolt(get_tree().current_scene, visual_origin, final_target)