PC3 Phase 1.4-1.6: avatars wired into the game end to end

- api_client.gd: get_avatar_loadout() / save_avatar_loadout()
- main_menu.gd: on successful auth (fresh or session-restore), load the
  catalog + fetch the saved loadout into AvatarSystem so the in-world
  player renders as the player's avatar. Best-effort: a slow/failed prime
  never gates getting in (UI goes authenticated first, prime runs after).
  New "Customize Avatar" button (enabled only when signed in).
- avatar_system.gd: local-player convenience API -- ensure_catalog(),
  set_loadout_from_dict() (from the backend's GET shape), has_loadout(),
  build_current_avatar().
- player.gd: swaps the placeholder capsule for the assembled avatar
  (feet-aligned to the capsule bottom) when a loadout is primed; silent
  fallback to the capsule otherwise. Camera stays first-person for now
  (third-person is a noted follow-up).
- avatar_visualizer.gd: rewrote it -- the old version referenced
  AvatarLoader.SlotResult / load_slot() which never existed, so it didn't
  compile and took avatar_customization_ui.gd down with it. Now a thin
  wrapper over AvatarLoader for the preview.
- avatar_customization_ui.gd: seeds from the live loadout, saves through to
  AvatarSystem + PUT /api/avatar/loadout (local file kept as fallback),
  fixed a Camera3D.look_at() before-in-tree crash.
- scenes/avatar_customization.tscn rebuilt (old one used the Godot-3
  `ViewportContainer` node type) + avatar_customization_screen.gd wrapper
  that returns to the menu on close.
- smoke_test_avatar_in_world.gd: primed loadout -> game.tscn -> player
  shows the assembled avatar, capsule hidden, rig + bone mounts present.

Verified: cold-cache smokes green (player 15/15, avatar_system 14/14,
avatar_in_world 10/10, main_menu_ui 13/13); against a live backend
main_menu_full_flow 12/12, main_menu_back 20/20, world_list 4/4,
enter_world 9/9, e2e 4/4; plus a manual register->default-loadout->
customize->save->re-fetch-persisted round trip.

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

scripts/avatar/avatar_customization_ui.gd

@@ -106,9 +106,14 @@ func _ready() -> void:
 	# Build the UI.
 	_build_ui()
 
-	# Create a fresh loadout.
-	loadout = AvatarLoadout.new()
-	loadout.base_body = default_base_body
+	# Seed from the player's live loadout (set at login) if there is one, so
+	# the screen opens showing what they're actually wearing; otherwise start
+	# from a bare default.
+	if _system != null and _system.current_loadout != null:
+		loadout = AvatarLoadout.from_json(_system.current_loadout.to_json())
+	if loadout == null or not loadout.validate():
+		loadout = AvatarLoadout.new()
+		loadout.base_body = default_base_body
 
 	# Initialize the visualizer.
 	_visualizer = AvatarVisualizer.new()
@@ -165,8 +170,9 @@ func _build_ui() -> void:
 	# Camera for the preview.
 	_preview_camera = Camera3D.new()
 	_preview_camera.name = "PreviewCamera"
-	_preview_camera.position = Vector3(0, 1.0, 3.0)
-	_preview_camera.look_at(Vector3(0, 1.0, 0))
+	# 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)
 	_preview_viewport.add_child(_preview_camera)
 
 	# Avatar root inside the viewport.
@@ -429,14 +435,26 @@ func _on_skin_tone_changed(value: float) -> void:
 func _on_save_pressed() -> void:
 	if loadout == null:
 		return
+
+	# Local cache (offline fallback / fast reopen).
 	var json := loadout.to_json()
 	var file := FileAccess.open("user://loadout.json", FileAccess.WRITE)
 	if file:
 		file.store_string(json)
 		file.close()
-		_status_label.text = "Loadout saved."
+
+	# Apply to the live in-world avatar immediately.
+	if _system != null:
+		_system.set_loadout_from_dict(JSON.parse_string(json))
+
+	# Persist to the backend if we're signed in.
+	var api := get_node_or_null("/root/ApiClient")
+	if api != null and api.has_token():
+		_status_label.text = "Saving…"
+		var res: Dictionary = await api.save_avatar_loadout(JSON.parse_string(json))
+		_status_label.text = "Saved." if res.get("ok", false) else "Saved locally (backend: %s)" % res.get("detail", "error")
 	else:
-		_status_label.text = "Failed to save loadout."
+		_status_label.text = "Saved locally (not signed in)."
 
 
 func _on_load_pressed() -> void: