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)

addons/netfox.extras/physics/rapier_driver_3d.gd.off

@@ -0,0 +1,18 @@
+extends PhysicsDriver
+
+class_name RapierDriver3D
+
+func _init_physics_space() -> void:
+	physics_space = get_viewport().world_3d.space
+	PhysicsServer3D.space_set_active(physics_space, false)
+
+func _physics_step(delta) -> void:
+	RapierPhysicsServer3D.space_step(physics_space, delta)
+	RapierPhysicsServer3D.space_flush_queries(physics_space)
+	
+func _snapshot_space(tick: int) -> void:
+	snapshots[tick] = RapierPhysicsServer3D.export_binary(physics_space)
+
+func _rollback_space(tick) -> void:
+	if snapshots.has(tick):
+		RapierPhysicsServer3D.import_binary(physics_space, snapshots[tick])