40250 classic: parallel-dev checkpoint through increment 49 (W0 interface freeze)

Captures the uncommitted parallel-development work (increments 46-49) on the
40250 classic client port, folded into docs/CLIENT-GAP.md + CLIENT-GAP-FIX.md.

Increment 49 (W0 interface-freeze batch, Phase 1 prerequisite) lands the
cross-workflow shared-file scaffolding so the 4 Phase 1 workflows can run in
isolated worktrees without contention:

- entity_store.{h,cpp}: Entity gains empire/affect_flags/owner_vid/state_flags;
  new mut_spawn_full() (single-shot two-packet merge, §2.3), mut_ownership()
  (§2.5), mut_map_bgm() + take_bgm_dirty()/bgm_name()/bgm_volume() (§9.1),
  drain_dirty() (§2.1/§2.5 bare-field-update queue); mut_char_info() now stores
  empire; reset_for_map_change() clears m_dirty.
- m2_client.cpp: new bgm_changed(name, volume) signal; classic + m2dev pump
  loops drain drain_dirty() -> entity_info and take_bgm_dirty() -> bgm_changed;
  entity_dict() exposes the 4 new keys.
- classic/classic_parser.{h,cpp}: GC_MAIN_CHARACTER3_BGM /
  GC_MAIN_CHARACTER4_BGM_VOL route bgm_name/bgm_volume to mut_map_bgm() (was
  discarded); new m_pending_actor staging map (W1 fills §2.2 merge logic).
- project/bgm_director.gd (new) + game_scene.gd: BGM consumption split out of
  net_world.gd so W2/W4 don't collide; §8.6/§4.8 keybind convergence (digits
  1-4 -> quickslots 0-3, F1-F4 -> quickslots 4-7, Ctrl+1..9 -> _emote()).

Tests: cmake --build build clean; ctest 16/16; 15 GDScript regressions green
(netbridge, gamescene, netplay, p9, p10, p2b, p8, system_menu_ui, skill,
combat_fx, skill_fx, player_motion, char_status_ui, chat, inventory), no skips.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014yvAPqPivoY7vmBbzgqK4W

project/app_flow.gd

@@ -1,19 +1,18 @@
 # AppFlow (P10) —— 登录 → 选人 → 进游戏 的串场控制器。
 #
-#   把它做场景根：一个 M2Client 贯穿全程，LoadingScreen / ReconnectUI 常驻。
+#   把它做场景根：一个 M2Client 贯穿全程，LoadingScreen 常驻。
 #   var af := preload("res://app_flow.gd").new()
 #   add_child(af)
 #   af.start(assets_root)          # assets_root 传给 game_scene
 #
 # 状态机：LOGIN → SELECT → GAME。M2Client 信号驱动切屏。
-# 断线：在 GAME 里保留场景交给 ReconnectUI 自动重连；在 LOGIN/SELECT 回登录。
+# 断线：任何阶段都回到登录阶段，和 ClientVS22 的 SetLoginPhase 一致。
 extends Node
 
 const ServerInfoRes = preload("res://net/serverinfo.gd")
 const ChannelStatus = preload("res://net/channel_status.gd")
 const LoadingScreen = preload("res://ui/loading_screen.gd")
 const CharSelectScreen = preload("res://ui/char_select_screen.gd")
-const ReconnectUI = preload("res://ui/reconnect_ui.gd")
 const GameScene = preload("res://game_scene.gd")
 
 enum { LOGIN, SELECT, GAME }
@@ -24,7 +23,6 @@ var _state := LOGIN
 var _assets := ""
 var _ui: CanvasLayer            # 登录 / 选人的临时界面层
 var _loading: CanvasLayer
-var _reconnect: CanvasLayer
 var _game: Node
 var build_game_scene := true    # 测试里置 false，只跑状态机不建重场景
 var _sel_server := 0
@@ -53,9 +51,6 @@ func start(assets_root: String = "", injected_client: Node = null) -> void:
 	_loading = LoadingScreen.new()
 	add_child(_loading)
 	_loading.setup(client)
-	_reconnect = ReconnectUI.new()
-	add_child(_reconnect)
-	_reconnect.setup(client)
 	_goto_login()
 	if auto_login:
 		call_deferred("_do_connect")
@@ -83,8 +78,12 @@ func _on_char_list(list: Array) -> void:
 			sc.set_chars(list)
 			return
 	_goto_select()
-	if auto_login and not _chars.is_empty() and client.has_method("select_character"):
-		client.select_character(int(_chars[0].get("index", 0)))
+	if auto_login and not _chars.is_empty():
+		var idx := int(_chars[0].get("index", 0))
+		if client.has_method("enter_game"):
+			client.enter_game(idx)
+		elif client.has_method("select_character"):
+			client.select_character(idx)
 
 func _on_char_name_changed(pid: int, name: String) -> void:
 	var sc: Node = _ui.get_node_or_null("CharSelect") if _ui and _state == SELECT else null
@@ -121,11 +120,9 @@ func _on_login_failed(reason: String) -> void:
 		_goto_login()
 		_set_status("登录失败：%s" % reason)
 
-func _on_disconnected(_reason: String) -> void:
-	# GAME 里：保留 game_scene，ReconnectUI 负责重连遮罩
-	# LOGIN/SELECT 里：回登录
-	if _state != GAME:
-		_goto_login()
+func _on_disconnected(reason: String) -> void:
+	_goto_login()
+	_set_status("连接断开：%s" % reason)
 
 # --- 切屏 ------------------------------------------------------------------
 
@@ -323,7 +320,9 @@ func _build_char_list() -> void:
 	_ui.add_child(screen)
 	screen.setup(client, _assets, _chars)
 	screen.select_requested.connect(func(idx: int):
-		if client.has_method("select_character"):
+		if client.has_method("enter_game"):
+			client.enter_game(idx)
+		elif client.has_method("select_character"):
 			client.select_character(idx))
 	screen.back_requested.connect(func():
 		if client.has_method("disconnect_from_server"):