Save workspace artifacts: character-controller, gdextension scaffold, network scripts, map-pipeline, server config

Includes code from task workspaces that was never pushed:
- client/characters/ — fps_character_controller.gd (400 lines), fps_camera.gd, input_handler.gd
- gdextension/simulation/ — C++ GDExtension scaffold: entity, movement, hit detection, simulation server, state serializer, bitstream (14 files)
- scripts/network/ — ENet-based network_manager.gd, server/client_main.gd, player.gd
- scripts/map_packaging/ — PCK pipeline: pack_map.gd, map_downloader.gd, map_registry_server.py, README
- scripts/config/ — server_config.gd (480 lines)
- scenes/ — client_main, server_main, player, test_range
- project.godot, export_presets.cfg

scenes/player.tscn

@@ -0,0 +1,15 @@
+[gd_scene format=3 uid="uid://player"]
+
+[ext_resource type="Script" path="res://scripts/network/player.gd" id="1_player"]
+
+[sub_resource type="BoxMesh" id="1"]
+size = Vector3(1, 1, 1)
+
+[node name="Player" type="Node3D"]
+script = ExtResource("1_player")
+movement_speed = 5.0
+sync_rate = 10.0
+
+[node name="Mesh" type="MeshInstance3D" parent="."]
+transform = Transform3D(1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0.5, 0)
+mesh = SubResource(1)