chore(multiplayer): Phase 0 refactors + graphics/perf settings groundwork

Lands the non-networked Phase 0 tasks from multiplayer-todo.md (ship/camera/
arena refactors, sim constants, background FPS handling) plus a first pass
at exposing graphics/performance settings (presets, resolution scaling,
vsync, FPS cap, perf overlay) and a GPU profiling harness for the
real-hardware follow-up in task 0.15b.

Game/scripts/ship.gd

@@ -1,5 +1,6 @@
 class_name Ship
 extends RigidBody3D
+const SimConstants = preload("res://scripts/sim_constants.gd")
 
 # Physics-driven spaceship. All movement is force/torque-based, applied in
 # _integrate_forces from a ShipAction supplied by a pluggable ShipController
@@ -44,7 +45,8 @@ extends RigidBody3D
 # Non-tinted hull meshes, runtime-merged into one ArrayMesh by
 # _build_merged_hull() (Nose/TailFin stay separate MeshInstance3Ds since
 # _apply_team_color() retints them per-team and must keep addressing them by
-# name). Verified via get_surface_count()/surface_get_material() before
+# name, under $Visual — see that function). Verified via
+# get_surface_count()/surface_get_material() before
 # writing this: hull and canopy are each a single surface with their own
 # distinct opaque StandardMaterial3D (canopy is NOT alpha/transparent despite
 # the name), and engine_l/engine_r are each 2 surfaces, also all distinct
@@ -105,6 +107,43 @@ var _current_action: ShipAction = ShipAction.new()
 var _inert_action: ShipAction = ShipAction.new()
 var _boundary: ArenaBoundary
 
+var _pending_teleport: Transform3D
+var _has_pending_teleport := false
+
+
+# Queues an authoritative teleport, applied at the top of the next
+# _integrate_forces — the only Jolt-safe place to write state.transform
+# directly (see GameMode._reset_body / task 0.15) — instead of racing the
+# physics step via set_deferred("global_transform", ...).
+func queue_teleport(to: Transform3D) -> void:
+	_pending_teleport = to
+	_has_pending_teleport = true
+
+
+# --- Netcode correction hooks (Phase 4; see multiplayer-todo.md §4.4) ---
+# Both stay zero until Phase 4 wires a reconciliation pass in, so the guarded
+# hook in _integrate_forces below is a no-op today.
+# Velocity delta from a soft correction, consumed once then cleared —
+# applied in full immediately (invisible to the player, and it's the
+# *cause* of future position error, so blending it just prolongs
+# divergence).
+var net_vel_correction := Vector3.ZERO
+# Rendered offset between the body and $Visual while a soft correction
+# decays away, so a position correction moves the collider in full without
+# visibly teleporting the mesh. Same decay convention as drag/righting
+# torque (_tick_scaled) above.
+var net_visual_offset := Vector3.ZERO
+const NET_VISUAL_OFFSET_DECAY := 0.88
+
+
+# Feeds thrust_z/turbo into the movement VFX for a ship with no local
+# controller driving _integrate_forces (a frozen remote ship never calls
+# get_action(), so _update_movement_vfx's engine glow/flame would otherwise
+# read a stale or zeroed action and show dead engines).
+func set_visual_action(thrust_z: float, turbo: bool) -> void:
+	_current_action.thrust.z = thrust_z
+	_current_action.turbo = turbo
+
 # Instrument signals for efficient data distribution
 signal speed_changed(speed: float)
 signal attitude_changed(pitch: float, roll: float, yaw: float)
@@ -135,6 +174,13 @@ var _engine_cores: Array[MeshInstance3D] = []
 var _engine_flames: Array[MeshInstance3D] = []
 var _engine_lights: Array[OmniLight3D] = []
 
+# All rendered geometry (hull, canopy, engine cores/flames/lights, Nose,
+# TailFin) parents under this instead of the RigidBody3D directly, so a
+# future prediction correction (task 0.14) can offset the visual without
+# moving the collider — see multiplayer-todo.md task 0.2. CollisionShape3D
+# and the controller child correctly stay on the body itself.
+@onready var visual: Node3D = $Visual
+
 
 func _ready():
 	# Add ship to group for instrument discovery
@@ -177,7 +223,7 @@ func _apply_team_color() -> void:
 		return
 	var accent := _get_team_material(team)
 	for mesh_name in ["Nose", "TailFin"]:
-		var mesh := get_node_or_null(mesh_name) as MeshInstance3D
+		var mesh := get_node_or_null("Visual/" + mesh_name) as MeshInstance3D
 		if mesh:
 			mesh.material_override = accent
 
@@ -205,7 +251,7 @@ func _build_merged_hull() -> void:
 	var instance := MeshInstance3D.new()
 	instance.name = "MergedHull"
 	instance.mesh = mesh
-	add_child(instance)
+	visual.add_child(instance)
 
 
 # Attach the node that drives this ship (player, AI, or network). Replaces
@@ -238,7 +284,7 @@ func _build_movement_vfx() -> void:
 		core.position = engine_pos
 		core.mesh = core_mesh
 		core.cast_shadow = GeometryInstance3D.SHADOW_CASTING_SETTING_OFF
-		add_child(core)
+		visual.add_child(core)
 		_engine_cores.append(core)
 
 		# A single conventional orange flame replaces the layered particle plume
@@ -265,7 +311,7 @@ func _build_movement_vfx() -> void:
 		flame.mesh = flame_mesh
 		flame.visible = false
 		flame.cast_shadow = GeometryInstance3D.SHADOW_CASTING_SETTING_OFF
-		add_child(flame)
+		visual.add_child(flame)
 		_engine_flames.append(flame)
 
 		var light := OmniLight3D.new()
@@ -275,7 +321,7 @@ func _build_movement_vfx() -> void:
 		light.omni_range = 3.5
 		light.omni_attenuation = 2.0
 		light.shadow_enabled = false
-		add_child(light)
+		visual.add_child(light)
 		_engine_lights.append(light)
 
 func _vfx_material(color: Color, energy: float) -> StandardMaterial3D:
@@ -343,6 +389,25 @@ func _has_telemetry_listeners() -> bool:
 
 
 func _integrate_forces(state):
+	if _has_pending_teleport:
+		_has_pending_teleport = false
+		state.transform = _pending_teleport
+		state.linear_velocity = Vector3.ZERO
+		state.angular_velocity = Vector3.ZERO
+		reset_physics_interpolation()
+
+	# --- Netcode correction hook (Phase 4) --- guarded: both fields default
+	# to Vector3.ZERO and nothing writes them yet, so neither branch runs
+	# today.
+	if net_vel_correction != Vector3.ZERO:
+		state.linear_velocity += net_vel_correction
+		net_vel_correction = Vector3.ZERO
+	if net_visual_offset != Vector3.ZERO:
+		net_visual_offset *= _tick_scaled(NET_VISUAL_OFFSET_DECAY, state.step)
+		if net_visual_offset.length_squared() < 0.0001:
+			net_visual_offset = Vector3.ZERO
+		visual.position = net_visual_offset
+
 	# One action per physics tick, pulled from the controller (deterministic)
 	_current_action = controller.get_action() if controller else _inert_action
 
@@ -448,7 +513,7 @@ func apply_rotation_forces(state: PhysicsDirectBodyState3D, rotation_input: Vect
 # by the actual elapsed tick time `step`, so `v *= _tick_scaled(k, step)`
 # decays at the same rate per second regardless of physics_ticks_per_second.
 func _tick_scaled(k: float, step: float) -> float:
-	return pow(k, step * 60.0)
+	return pow(k, step * SimConstants.TICK_HZ)
 
 
 func apply_drag_and_limits(state: PhysicsDirectBodyState3D, rotation_input: Vector3):