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/weapon/network-weapon-3d.gd

@@ -0,0 +1,75 @@
+extends Node3D
+class_name NetworkWeapon3D
+
+## A 3D-specific implementation of [NetworkWeapon].
+
+## Distance to consider too large during reconciliation checks.
+@export var distance_threshold: float = 1.0
+
+var _weapon: _NetworkWeaponProxy
+
+func can_fire() -> bool:
+	return _weapon.can_fire()
+
+func fire() -> Node3D:
+	return _weapon.fire()
+
+func get_fired_tick() -> int:
+	return _weapon.get_fired_tick()
+
+func _init():
+	_weapon = _NetworkWeaponProxy.new()
+	add_child(_weapon, true, INTERNAL_MODE_BACK)
+	_weapon.owner = self
+	
+	_weapon.c_can_fire = _can_fire
+	_weapon.c_can_peer_use = _can_peer_use
+	_weapon.c_after_fire = _after_fire
+	_weapon.c_spawn = _spawn
+	_weapon.c_get_data = _get_data
+	_weapon.c_apply_data = _apply_data
+	_weapon.c_is_reconcilable = _is_reconcilable
+	_weapon.c_reconcile = _reconcile
+
+
+## See [NetworkWeapon]
+func _can_fire() -> bool:
+	return false
+
+## See [NetworkWeapon]
+func _can_peer_use(peer_id: int) -> bool:
+	return true
+
+## See [NetworkWeapon]
+func _after_fire(projectile: Node3D):
+	pass
+
+## See [NetworkWeapon]
+func _spawn() -> Node3D:
+	return null
+
+func _get_data(projectile: Node3D) -> Dictionary:
+	return {
+		"global_transform": projectile.global_transform
+	}
+
+func _apply_data(projectile: Node3D, data: Dictionary):
+	projectile.global_transform = data["global_transform"]
+
+func _is_reconcilable(projectile: Node3D, request_data: Dictionary, local_data: Dictionary) -> bool:
+	var req_transform = request_data["global_transform"] as Transform3D
+	var loc_transform = local_data["global_transform"] as Transform3D
+	
+	var request_pos = req_transform.origin
+	var local_pos = loc_transform.origin
+	
+	return request_pos.distance_to(local_pos) < distance_threshold
+
+func _reconcile(projectile: Node3D, local_data: Dictionary, remote_data: Dictionary):
+	var local_transform = local_data["global_transform"] as Transform3D
+	var remote_transform = remote_data["global_transform"] as Transform3D
+
+	var relative_transform = projectile.global_transform * local_transform.inverse()
+	var final_transform = remote_transform * relative_transform
+	
+	projectile.global_transform = final_transform