Third-person camera + fix the avatar customize preview

You couldn't see your own character because the camera was first-person
(inside the avatar's head), and the customize screen's 3D preview rendered
nothing.

- player.tscn: camera now hangs off a SpringArm3D on a CameraPivot, 4 m
  behind + above the player, pulled in on collision. player.gd: yaw still
  turns the body, pitch orbits the arm (starts tilted down to frame the
  avatar).
- avatar_customization_ui.gd: the preview SubViewport had own_world_3d=false,
  so it shared the Control-only main world -- no scenario, nothing rendered.
  Set own_world_3d=true, add a WorldEnvironment with ambient fill + a
  key/fill light pair, make the camera current, tweak framing.
- smoke_test_player: assert the third-person SpringArm rig (18/18).
- smoke_test_enter_world: wait longer for the scene change -- a real
  POST /join spawns a dedicated server, which is slow (9/9).

Client-side change -- rebuild the exe to get it.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015jtxAiu5dAW4WxCNdGkrkJ

scripts/avatar/avatar_customization_ui.gd

@@ -165,14 +165,31 @@ func _build_ui() -> void:
 	_preview_viewport.name = "PreviewViewport"
 	_preview_viewport.size = Vector2i(464, 560)
 	_preview_viewport.render_target_update_mode = SubViewport.UPDATE_ALWAYS
+	_preview_viewport.transparent_bg = true
+	# Its own 3D world -- a SubViewport that shares the (Control-only) main
+	# world has no scenario/environment set up and renders nothing.
+	_preview_viewport.own_world_3d = true
 	_preview_container.add_child(_preview_viewport)
 
+	# Environment: ambient fill so the model reads even from a bad light angle.
+	var world_env := WorldEnvironment.new()
+	world_env.name = "PreviewEnv"
+	var env := Environment.new()
+	env.background_mode = Environment.BG_COLOR
+	env.background_color = Color(0.10, 0.11, 0.14)
+	env.ambient_light_source = Environment.AMBIENT_SOURCE_COLOR
+	env.ambient_light_color = Color(0.6, 0.6, 0.65)
+	env.ambient_light_energy = 1.0
+	world_env.environment = env
+	_preview_viewport.add_child(world_env)
+
 	# Camera for the preview.
 	_preview_camera = Camera3D.new()
 	_preview_camera.name = "PreviewCamera"
 	# look_at needs a global transform, which only exists once in the tree.
 	_preview_camera.look_at_from_position(
-		Vector3(0, 1.0, 3.0), Vector3(0, 1.0, 0), Vector3.UP)
+		Vector3(0, 1.0, 3.2), Vector3(0, 0.9, 0), Vector3.UP)
+	_preview_camera.current = true
 	_preview_viewport.add_child(_preview_camera)
 
 	# Avatar root inside the viewport.
@@ -180,11 +197,17 @@ func _build_ui() -> void:
 	_preview_root.name = "AvatarPreviewRoot"
 	_preview_viewport.add_child(_preview_root)
 
-	# A light so the avatar is visible.
-	var light := DirectionalLight3D.new()
-	light.name = "PreviewLight"
-	light.rotation_degrees = Vector3(-45, 30, 0)
-	_preview_viewport.add_child(light)
+	# Key + fill lights so the avatar is clearly visible.
+	var key := DirectionalLight3D.new()
+	key.name = "PreviewKeyLight"
+	key.rotation_degrees = Vector3(-35, 35, 0)
+	key.light_energy = 1.2
+	_preview_viewport.add_child(key)
+	var fill := DirectionalLight3D.new()
+	fill.name = "PreviewFillLight"
+	fill.rotation_degrees = Vector3(-20, -140, 0)
+	fill.light_energy = 0.4
+	_preview_viewport.add_child(fill)
 
 	# --- Right: controls ---
 	var controls_panel := PanelContainer.new()