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/physics-driver-toggles.gd

@@ -0,0 +1,88 @@
+extends Object
+
+class PhysicsDriverToggle:
+	const INACTIVE_SUFFIX := ".off"
+
+	func get_name() -> String:
+		return "???"
+
+	func get_files() -> Array[String]:
+		return []
+
+	func get_error_messages() -> Array[String]:
+		return []
+
+	func is_enabled() -> bool:
+		return get_files().any(func(it): return FileAccess.file_exists(it))
+
+	func toggle() -> Array[String]:
+		var errors := get_error_messages()
+		if not errors.is_empty():
+			return errors
+
+		var enable := not is_enabled()
+		
+		var uid_files := get_files().map(func(it): return it + ".uid")
+		var renames = (get_files() + uid_files).map(func(it):
+			if enable: return [it + INACTIVE_SUFFIX, it]
+			else: return [it, it + INACTIVE_SUFFIX]
+		)
+		
+		for rename in renames:
+			var result := DirAccess.rename_absolute(rename[0], rename[1])
+			if result != OK:
+				errors.append(
+					"Failed rename \"%s\" -> \"%s\"; reason: %s" %
+					[rename[0], rename[1], error_string(result)]
+				)
+		return errors
+
+class Rapier2DPhysicsDriverToggle extends PhysicsDriverToggle:
+	func get_name() -> String:
+		return "Rapier2D"
+
+	func get_files() -> Array[String]:
+		return [
+			"res://addons/netfox.extras/physics/rapier_driver_2d.gd",
+		]
+
+	func get_error_messages() -> Array[String]:
+		if not ClassDB.class_exists("RapierPhysicsServer2D"):
+			return ["Rapier physics is not available! Is the extension installed?"]
+		return []
+
+class Rapier3DPhysicsDriverToggle extends PhysicsDriverToggle:
+	func get_name() -> String:
+		return "Rapier3D"
+
+	func get_files() -> Array[String]:
+		return [
+			"res://addons/netfox.extras/physics/rapier_driver_3d.gd",
+		]
+
+	func get_error_messages() -> Array[String]:
+		if not ClassDB.class_exists("RapierPhysicsServer3D"):
+			return ["Rapier physics is not available! Is the extension installed?"]
+		return []
+
+class GodotPhysicsDriverToggle extends PhysicsDriverToggle:
+	func get_name() -> String:
+		return "Godot"
+
+	func get_files() -> Array[String]:
+		return [
+			"res://addons/netfox.extras/physics/godot_driver_3d.gd",
+			"res://addons/netfox.extras/physics/godot_driver_2d.gd"
+		]
+
+	func get_error_messages() -> Array[String]:
+		if not PhysicsServer3D.has_method("space_step") or not PhysicsServer2D.has_method("space_step"):
+			return ["Physics stepping is not available! Is this the right Godot build?"]
+		return []
+
+static func all() -> Array[PhysicsDriverToggle]:
+	return [
+		Rapier2DPhysicsDriverToggle.new(),
+		Rapier3DPhysicsDriverToggle.new(),
+		GodotPhysicsDriverToggle.new()
+	]