feat(ui): introduce MetaScreen pattern foundation (#618, #680)

Establishes the faux-game-menu base pattern for non-diegetic UI,
analogous to ImplantApp but for pre-gameplay and meta-overlay
screens (main menu, character creation, settings, debug console,
bug report, loading screen). Workstream 1 of the MetaScreen
refactor — foundation only, no screen migrations yet.

- client/ui/meta/meta_screen.gd: base class (Control) with
  HIDDEN/OPENING/OPEN/CLOSING phase tracking, three orthogonal
  policy booleans (pauses_sim, closable_by_escape, captures_input),
  open/close lifecycle, on_escape contract, closed + escape_pressed
  signals, subclass hooks (on_open, on_close).
- client/ui/meta/meta_stack.gd: autoload coordinator. Overlay stack
  with push/pop/top/is_active; handle_escape chain; sim-pause
  coordination via SimBridge when pauses_sim=true; meta_active_changed
  signal. All class references kept inside method bodies — no
  top-level class_name refs, matching HudGroups / GameState
  autoload parse-order discipline.
- client/scripts/character_profile.gd: Resource wrapping the
  visual descriptor with bookmark_id and start_location_id.
  Target of the creation_confirmed signal once the character
  creation flow migrates.
- client/project.godot: MetaStack registered as autoload after
  HudGroups, before ImplantRegistry.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

client/project.godot

@@ -29,6 +29,7 @@ FogState="*res://scripts/autoloads/fog_state.gd"
 AudioManager="*res://scripts/autoloads/audio_manager.gd"
 SessionManager="*res://scripts/autoloads/session_manager.gd"
 HudGroups="*res://scripts/autoloads/hud_groups.gd"
+MetaStack="*res://ui/meta/meta_stack.gd"
 ImplantRegistry="*res://ui/implant/implant_registry.gd"
 HardwareDetector="*res://ui/hardware_detector.gd"
 

client/scripts/character_profile.gd

@@ -0,0 +1,8 @@
+class_name CharacterProfile
+extends Resource
+## Collects all character creation choices into a single transferable object (#618).
+## Passed as the argument to character_creation's creation_confirmed signal.
+
+@export var descriptor: CharacterVisualDescriptor
+@export var bookmark_id: String = ""
+@export var start_location_id: String = ""

client/ui/meta/meta_screen.gd

@@ -0,0 +1,60 @@
+class_name MetaScreen
+extends Control
+## Base class for all meta-UI screens (#618, #680).
+## Scene-root screens (main_menu, character_creation) extend this for the
+## lifecycle contract. Overlay screens (settings, debug_console, bug_report,
+## loading_screen) extend this AND push onto MetaStack.
+
+signal closed
+signal escape_pressed
+
+enum Phase { HIDDEN, OPENING, OPEN, CLOSING }
+
+@export var pauses_sim: bool = false
+@export var closable_by_escape: bool = true
+@export var captures_input: bool = true
+
+var _phase: Phase = Phase.HIDDEN
+
+
+func open() -> void:
+	if _phase != Phase.HIDDEN:
+		return
+	_phase = Phase.OPENING
+	visible = true
+	if captures_input:
+		mouse_filter = Control.MOUSE_FILTER_STOP
+	on_open()
+	_phase = Phase.OPEN
+
+
+func close() -> void:
+	if _phase != Phase.OPEN:
+		return
+	_phase = Phase.CLOSING
+	on_close()
+	visible = false
+	_phase = Phase.HIDDEN
+	closed.emit()
+
+
+func is_open() -> bool:
+	return _phase == Phase.OPEN
+
+
+## Called by MetaStack when ESC is pressed with this screen on top.
+## Return true to consume the event (prevent stack pop); false to allow pop.
+func on_escape() -> bool:
+	escape_pressed.emit()
+	return false
+
+
+# --- Lifecycle hooks — subclasses override ---
+
+
+func on_open() -> void:
+	pass
+
+
+func on_close() -> void:
+	pass

client/ui/meta/meta_stack.gd

@@ -0,0 +1,72 @@
+extends Node
+## Autoload coordinator for overlay MetaScreens (#618, #680).
+## Scene-root screens (main_menu, character_creation) do NOT push onto this stack.
+## Only overlay screens (settings, debug_console, bug_report, loading_screen) push.
+##
+## Autoload parse-order: MetaScreen is a class_name type — referenced here only
+## inside method bodies called at runtime, never at the top level or in _ready().
+
+signal meta_active_changed(active: bool)
+
+var _stack: Array = []  # Array[MetaScreen] — untyped per parse-order rule
+
+
+func push(screen) -> void:  # screen: MetaScreen
+	if screen in _stack:
+		return
+	_stack.append(screen)
+	screen.closed.connect(_on_screen_closed.bind(screen), CONNECT_ONE_SHOT)
+	if _stack.size() == 1:
+		meta_active_changed.emit(true)
+	if screen.pauses_sim:
+		_request_pause(true)
+
+
+func pop() -> void:
+	if _stack.is_empty():
+		return
+	_stack[-1].close()
+
+
+func top():  # returns MetaScreen or null
+	return _stack[-1] if not _stack.is_empty() else null
+
+
+func is_active() -> bool:
+	return not _stack.is_empty()
+
+
+## Handle ESC key. Call from main.gd before HudGroups ESC handling.
+## Returns true if the event was consumed (callers must return after).
+func handle_escape() -> bool:
+	var t = top()
+	if t == null:
+		return false
+	if not t.closable_by_escape:
+		return t.on_escape()
+	if t.on_escape():
+		return true
+	t.close()
+	return true
+
+
+func _on_screen_closed(screen) -> void:  # screen: MetaScreen
+	_stack.erase(screen)
+	if screen.pauses_sim and not _any_pausing():
+		_request_pause(false)
+	if _stack.is_empty():
+		meta_active_changed.emit(false)
+
+
+func _any_pausing() -> bool:
+	for s in _stack:
+		if s.pauses_sim:
+			return true
+	return false
+
+
+func _request_pause(pause: bool) -> void:
+	if SimBridge.state != SimBridge.ConnectionState.CONNECTED:
+		return
+	var action = InputMapper.Action.PAUSE if pause else InputMapper.Action.UNPAUSE
+	SimBridge.send_input({"action": action, "timestamp_msec": Time.get_ticks_msec()})