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

gdextension/simulation/.gitignore

@@ -0,0 +1,19 @@
+# Build artifacts
+build/
+gdextension/bin/
+
+# IDE
+.idea/
+.vscode/
+*.swp
+*.swo
+*~
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Python
+__pycache__/
+*.pyc
+*.pyo