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)

scripts/network/player_net_input.gd.netfox-wip

@@ -0,0 +1,76 @@
+## PlayerNetInput — netfox BaseNetInput subclass for tactical-shooter.
+##
+## This node lives under the Player scene and gathers input each network
+## tick. RollbackSynchronizer references its properties in `input_properties`.
+##
+## Usage:
+##   Place as a child of the Player (CharacterBody3D or Node3D).
+##   The RollbackSynchronizer on the player's parent node will call
+##   _gather() before each tick, reading these exported properties.
+
+extends BaseNetInput
+class_name PlayerNetInput
+
+# ---------------------------------------------------------------------------
+# Input state — read by RollbackSynchronizer as input_properties
+# These are set in _gather() on the authority peer before every tick.
+# ---------------------------------------------------------------------------
+
+## Movement direction in local space (normalized, or zero).
+@export var move_direction: Vector3 = Vector3.ZERO
+
+## Mouse look: yaw (horizontal, radians).
+@export var look_yaw: float = 0.0
+
+## Mouse look: pitch (vertical, radians).
+@export var look_pitch: float = 0.0
+
+## Jump pressed this tick.
+@export var jump: bool = false
+
+## Sprint toggle active.
+@export var sprint: bool = false
+
+## Crouch toggle active.
+@export var crouch: bool = false
+
+## Shoot pressed this tick.
+@export var shoot: bool = false
+
+## Aim-down-sights pressed.
+@export var aim: bool = false
+
+# ---------------------------------------------------------------------------
+# Input gathering (called before each tick on the authority peer)
+# ---------------------------------------------------------------------------
+
+func _gather() -> void:
+	# Movement direction
+	var dir := Vector3.ZERO
+	if Input.is_action_pressed(&"move_forward") or Input.is_action_pressed(&"move_up"):
+		dir.z -= 1.0
+	if Input.is_action_pressed(&"move_backward") or Input.is_action_pressed(&"move_down"):
+		dir.z += 1.0
+	if Input.is_action_pressed(&"move_left"):
+		dir.x -= 1.0
+	if Input.is_action_pressed(&"move_right"):
+		dir.x += 1.0
+	if dir.length_squared() > 0.0:
+		dir = dir.normalized()
+	move_direction = dir
+
+	# Mouse look is handled in fps_character_controller.gd _input()
+	# and synced here via the character controller's current yaw/pitch.
+	# If this node has a FPSCharacterController sibling, read from it.
+	var parent := get_parent()
+	if parent and parent.has_method(&"get_current_yaw"):
+		look_yaw = parent.get_current_yaw()
+	if parent and parent.has_method(&"get_current_pitch"):
+		look_pitch = parent.get_current_pitch()
+
+	# Action inputs
+	jump = Input.is_action_just_pressed(&"jump")
+	sprint = Input.is_action_pressed(&"sprint")
+	crouch = Input.is_action_pressed(&"crouch")
+	shoot = Input.is_action_pressed(&"shoot")
+	aim = Input.is_action_pressed(&"aim")