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/player.gd

@@ -2,11 +2,10 @@ class_name Player
 extends CharacterBody3D
 ## The player character controller.
 ##
-## A simple CharacterBody3D with WASD/arrow locomotion, gravity, jump, and a
-## first-person Camera3D with mouse-look.  Reads the spawn point from the
-## current scene's `PlayerSpawn` Marker3D (see docs/architecture/pc2_test_level.md §3).
-##
-## No networking, no chunk code, no avatar UI — PC2 is local-only.
+## A CharacterBody3D with WASD/arrow locomotion, gravity, jump, and a
+## third-person camera (SpringArm3D behind the player) with mouse-look --
+## yaw turns the body, pitch orbits the camera. Reads the spawn point from
+## the current scene's `PlayerSpawn` Marker3D.
 
 
 # ---------------------------------------------------------------------------
@@ -20,23 +19,25 @@ const GRAVITY: float = 9.8
 ## Mouse-look sensitivity (radians per pixel of relative motion).
 const MOUSE_SENSITIVITY: float = 0.003
 
-## Camera pitch is clamped so the player can't flip past looking straight
-## up/down (which would otherwise let mouse-look invert on itself).
-const PITCH_LIMIT: float = deg_to_rad(89.0)
-
 
 # ---------------------------------------------------------------------------
 # Input state
 # ---------------------------------------------------------------------------
 
 var _input_direction := Vector2.ZERO
-var _camera_pitch: float = 0.0
+var _camera_pitch: float = -0.25
 
 ## Vertical offset applied to the assembled avatar so its feet (origin y=0)
 ## line up with the bottom of the player's collision capsule.
 const AVATAR_FEET_OFFSET: float = -0.8
 
-@onready var _camera: Camera3D = $Camera3D
+## Third-person pitch limits (radians): a bit up, a lot down (looking over
+## the avatar's shoulder toward the ground).
+const PITCH_MIN: float = -1.1
+const PITCH_MAX: float = 0.45
+
+@onready var _camera: Camera3D = $CameraPivot/SpringArm3D/Camera3D
+@onready var _camera_pivot: Node3D = $CameraPivot
 @onready var _capsule_mesh: MeshInstance3D = $CapsuleMesh
 
 var _avatar_view: Node3D = null
@@ -69,8 +70,11 @@ func _ready() -> void:
 		push_warning("player.gd: no PlayerSpawn marker found; spawning at origin")
 		global_position = Vector3(0, 1.0, 0)
 
-	# Capture the mouse for FPS-style look. Headless/test runs have no real
-	# window to capture input for, so guard against that rather than error.
+	# Start the camera arm tilted down a little so the avatar is framed.
+	_camera_pivot.rotation.x = _camera_pitch
+
+	# Capture the mouse for look. Headless/test runs have no real window to
+	# capture input for, so guard against that rather than error.
 	if DisplayServer.get_name() != "headless":
 		Input.mouse_mode = Input.MOUSE_MODE_CAPTURED
 
@@ -143,11 +147,11 @@ func _clear_input_direction(key: InputEventKey) -> void:
 
 func _handle_mouse_look(event: InputEventMouseMotion) -> void:
 	# Yaw rotates the whole body (so movement direction turns with the
-	# look direction); pitch only tilts the camera, so the capsule itself
-	# never tips over.
+	# look direction); pitch orbits the camera arm around the player, so the
+	# capsule itself never tips over.
 	rotation.y -= event.relative.x * MOUSE_SENSITIVITY
-	_camera_pitch = clampf(_camera_pitch - event.relative.y * MOUSE_SENSITIVITY, -PITCH_LIMIT, PITCH_LIMIT)
-	_camera.rotation.x = _camera_pitch
+	_camera_pitch = clampf(_camera_pitch - event.relative.y * MOUSE_SENSITIVITY, PITCH_MIN, PITCH_MAX)
+	_camera_pivot.rotation.x = _camera_pitch
 
 
 # ---------------------------------------------------------------------------