feat(client): Option A pre-game flow + ESC priority chain (Workstream 4)

main_menu now connects SimBridge before character_creation opens, gating
the transition on first ObserverSnapshot carrying a bookmark_catalog.
Loading screen is shown during the connect; on cancel the SimBridge
subprocess is torn down and the player returns to main_menu. Catalog is
read straight from GameState.bookmark_catalog in W6.

Flow (Option A):
1. New Game → SessionManager.new_game() creates save dir
2. main_menu pushes loading_screen via MetaStack with "Connecting to
   simulation..." message
3. SimBridge.connect_to_sim() spawned; main_menu listens on
   connection_state_changed, then on snapshot_received for the catalog
4. On catalog arrival: loading_screen closed, scene-transition to
   character_creation
5. character_creation Cancel → SimBridge.disconnect_from_sim() + scene
   transition back to main_menu (Tyre's recommendation: clean state per
   session over warm-start savings)
6. character_creation Start → ConfirmBookmark sent (stubbed for W4 with
   first catalog entry; real bookmark + location from W6's UI)

ESC priority chain in main.gd OPEN_MENU handler:
- MetaStack.handle_escape() first — closes the topmost meta overlay
- HudGroups.is_implant_active() / close_app() — closes active implant
- Fallback: toggle settings_dialog (existing W2 behavior)

Files:
- sim_bridge.gd: send_named_action(action_name, action_data) helper.
  Bridges named tag-enum PlayerActions (RequestBookmarkCatalog,
  ConfirmBookmark) into the existing outbound buffer, parallel to
  send_input's InputMapper.Action handling.
- loading_screen.gd: set_message(text) for the connecting/loading label.
- main_menu.gd: full Option A flow rewrite. Tracks _waiting_for_catalog
  so re-clicking New Game during connect is a no-op.
- character_creation.gd: _on_back disconnect path + _on_start
  ConfirmBookmark stub. MAIN_MENU_SCENE / GAME_SCENE constants.
- main.gd: connect_to_sim guard (don't reconnect when Option A leaves
  it CONNECTED). ESC chain wiring.

Verification:
- gdlint clean
- godot --headless --path client --quit — no SCRIPT ERROR
- test_protocol 62/62, test_implant_nav_stack 52/52, test_client_p3
  24/24, test_ui_framework_sprint15 54/54

Pre-existing failing suites unchanged: test_sprint2_proof,
test_dialogue_sprint18, test_client_p2 (camera-smoothing assertions
that pre-date W4 — main.gd has disabled position_smoothing_enabled
since #117 / #501 / #117 manual-lerp; tests were stale).

Workstream 5 (3-tab restructure of character_creation: Bookmark /
Appearance with sub-nav / Skills / Debug) lands next.

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

client/scripts/autoloads/sim_bridge.gd

@@ -387,6 +387,19 @@ func send_input(player_input: Dictionary) -> Error:
 	return OK
 
 
+## Queue a named PlayerAction by wire string (e.g. "RequestBookmarkCatalog").
+## For use outside the input event loop — protocol-level requests that aren't
+## bound to an InputMapper.Action enum value.
+func send_named_action(action_name: String, action_data: Variant = null) -> void:
+	if state != ConnectionState.CONNECTED:
+		push_warning("SimBridge.send_named_action(%s): not connected" % action_name)
+		return
+	var entry: Dictionary = {"tick": GameState.current_tick, "action_name": action_name}
+	if action_data != null:
+		entry["action_data"] = action_data
+	_outbound_buffer.append(entry)
+
+
 # Poll for snapshot from simulation.
 # In test mode delegates to test harness. In live mode, returns the last decoded snapshot.
 func poll_snapshot() -> Variant:

client/scripts/main.gd

@@ -47,8 +47,10 @@ func _ready() -> void:
 	# #117: Manual lerp approach — disable Godot's built-in Camera2D smoothing.
 	camera.position_smoothing_enabled = false
 
-	# Connect to simulation (test mode sets CONNECTED immediately)
-	SimBridge.connect_to_sim()
+	# Connect to simulation (test mode sets CONNECTED immediately).
+	# Guard: Option A flow leaves SimBridge CONNECTED when main.tscn loads — don't drop it.
+	if SimBridge.state == SimBridge.ConnectionState.DISCONNECTED:
+		SimBridge.connect_to_sim()
 
 	# #257: Deferred load dispatch
 	if not GameState.pending_load_path.is_empty():
@@ -265,8 +267,13 @@ func _process(delta: float) -> void:
 			elif err != OK:
 				push_error("main.gd: LOAD_GAME send_input failed: %s" % error_string(err))
 			continue
-		# #528: ESC/OPEN_MENU — client-only, toggle audio settings dialog
+		# #528: ESC/OPEN_MENU — priority chain: MetaStack modal → implant app → settings dialog
 		if input.action == InputMapper.Action.OPEN_MENU:
+			if MetaStack.handle_escape():
+				continue
+			if HudGroups.is_implant_active():
+				HudGroups.close_app()
+				continue
 			if settings_dialog:
 				if settings_dialog.is_open():
 					settings_dialog.close()