Phase 7: netfox + godot-jolt stack upgrade

Stack installed:
- netfox v1.35.3 (core + extras + noray + internals)
- godot-jolt v0.16.0-stable

Architecture:
- Server: ENet transport (works headless, no netfox deps)
- Client/Editor: netfox rollback (RollbackSynchronizer, TickInterpolator)

New/modified:
- docs/migration-netfox-plan.md — migration architecture
- scripts/network/network_manager.gd — netfox-aware ENet fallback
- scripts/network/player.gd — clean base player
- client/characters/player_netfox.gd — rollback player w/ WeaponManager
- client/characters/input/player_net_input.gd — BaseNetInput subclass
- client/characters/character/fps_character_controller.gd — netfox input feed
- client/weapons/ — weapon data, registry, TacticalWeaponHitscan, WeaponManager
- client/scripts/round_replicator.gd — client-side round state bridge
- server/scripts/round_manager.gd — improved state machine
- server/scripts/plugin_api/plugin_manager.gd — refined plugin system
- config: enemy_tag, ally_tag for meatball targeting

Removed: old C++ SimulationServer GDExtension (replaced by netfox rollback)

project.godot

@@ -20,11 +20,21 @@ config/features=PackedStringArray("4.7", "Forward Plus")
 NetworkManager="*res://scripts/network/network_manager.gd"
 ServerConfig="*res://scripts/config/server_config.gd"
 PluginManager="*res://server/scripts/plugin_api/plugin_manager.gd"
+RoundManager="*res://server/scripts/round_manager.gd"
+NetfoxBootstrap="*res://scripts/network/netfox_bootstrap.gd"
 
 [physics]
 
 common/physics_ticks_per_second=128
 common/enable_pause_aware_picking=true
+3d/physics_engine="Jolt3D"
+
+[plugins]
+
+netfox="CUSTOM"
+netfox.extras="CUSTOM"
+netfox.noray="CUSTOM"
+godot-jolt="CUSTOM"
 
 [rendering]