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/hitscan_tracer.gd

@@ -6,6 +6,41 @@ var target_position: Vector3
 var distance_traveled: float = 0.0
 var max_distance: float = 0.0
 
+
+## Spawn a cel-styled tracer bolt: unshaded hot core with an ink outline,
+## flying from origin to target. Shared by every hitscan weapon and the
+## remote-fire replay so all bullets look on-theme.
+static func spawn_bolt(scene: Node, origin: Vector3, target: Vector3,
+		color: Color = Color(1.0, 0.72, 0.15)) -> void:
+	if scene == null or origin.distance_squared_to(target) <= 0.1:
+		return
+	var tracer := HitscanTracer.new()
+
+	var core := MeshInstance3D.new()
+	var core_mesh := CapsuleMesh.new()
+	core_mesh.radius = 0.025
+	core_mesh.height = 1.1
+	var m := StandardMaterial3D.new()
+	m.shading_mode = BaseMaterial3D.SHADING_MODE_UNSHADED
+	m.albedo_color = color.lightened(0.35)
+	m.emission_enabled = true
+	m.emission = color
+	m.emission_energy_multiplier = 2.2
+	core_mesh.material = m
+	core.mesh = core_mesh
+	core.rotation.x = deg_to_rad(90) # orient capsule along Z
+	core.position = Vector3(0, 0, -0.55) # tail sits at the origin
+	core.material_overlay = LevelMaterials.outline(0.012)
+	tracer.add_child(core)
+
+	tracer.position = origin
+	tracer.target_position = target
+	scene.add_child(tracer)
+	var up := Vector3.UP
+	if absf((target - origin).normalized().dot(up)) > 0.99:
+		up = Vector3.RIGHT
+	tracer.look_at(target, up)
+
 func _ready() -> void:
 	max_distance = global_position.distance_to(target_position)
 	if max_distance < 0.1: