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)

client/characters/character/fps_camera.gd

@@ -51,8 +51,8 @@ extends Camera3D
 # Internal
 # ---------------------------------------------------------------------------
 
-## Reference to parent controller.
-var _controller: FPSCharacterController = null
+## Reference to parent controller (duck-typed — uses has_method instead of class_name).
+var _controller: Node = null
 
 ## Bob time accumulator.
 var _bob_time: float = 0.0
@@ -82,9 +82,9 @@ var _base_eye_y: float = 0.0
 # ---------------------------------------------------------------------------
 
 func _ready() -> void:
-	_controller = get_parent() as FPSCharacterController
-	if _controller == null:
-		push_warning("FpsCamera: Parent is not an FPSCharacterController. View features disabled.")
+	_controller = get_parent()
+	if _controller == null or not _controller.has_method(&"is_sprinting"):
+		push_warning("FpsCamera: Parent has no is_sprinting() — view features disabled.")
 
 	_base_fov = fov
 
@@ -172,9 +172,9 @@ func _update_bob(delta: float) -> void:
 func _update_sway(delta: float) -> void:
 	# Sway follows mouse movement indirectly via controller yaw/pitch changes
 	# Use velocity for physics-based sway: recentre over time
-	var vel: Vector3 = _controller.velocity
-	var sway_h := clamp(vel.x * 0.003, -sway_max_rotation, sway_max_rotation)
-	var sway_v := clamp(vel.z * 0.003, -sway_max_rotation, sway_max_rotation)
+	var vel := _controller.velocity as Vector3
+	var sway_h: float = clamp(vel.x * 0.003, -sway_max_rotation, sway_max_rotation)
+	var sway_v: float = clamp(vel.z * 0.003, -sway_max_rotation, sway_max_rotation)
 	# Add a tiny amount from pitch/yaw delta (not mouse, from movement direction change)
 	_sway_target = Vector2(
 		move_toward(_sway_target.x, sway_h, sway_response * delta),