feat(playable): 首个 Mac 联网内测版 STB-01 soak 工具与发布状态文档

- 新增 script/playable_soak.sh：先做 soak 配置/资源校验，无 --allow-gameplay
  只校验不启动客户端；N(>=10) 次独立正常退出运行 + 墙钟 soak，失败即停止后续
  运行并记 BLOCKED；写本批次 release-manifest.json 后聚合
- run_client_gate.sh：确认的故障代理对所有 suite 启动（共享场景的退出运行也经代理）；
  soak 超时下限只约束 soak 客户端（validate_soak 增加 soak_client 参数）
- 新增本地 127.0.0.1 故障代理、RSS 采样/内存判定、窗口/指标/流程模块及其测试
- forest_mob_render_test 输出 PASS/FAIL 标记，供 rendering_batch_test.sh 识别
- 新增 docs/FIRST-MAC-PLAYABLE-STATUS.md：如实记录 PASS/BLOCKED、已知问题与环境需求
- .gitignore 排除本地场景配置、凭据文件与运行输出

离线回归：rendering_batch_test.sh failures=0，playable_gate_test.sh PASS，
node 夹具测试 PASS。未联网运行，未重建候选包。

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ft3kXpNdLbKEfg5uDLfqVF

project/app_flow_lifecycle_test.gd

@@ -74,6 +74,20 @@ func _init() -> void:
 	_ck(game_snapshot.get("stage", "") == "GAME" and not game_snapshot.get("reconnecting", true),
 			"playable snapshot reports GAME after reconnect")
 
+	# Auto-login with an explicit MT_CHAR_SLOT must never fall back to another
+	# character, and the chosen slot must be remembered for a later reconnect.
+	flow._state = AppFlow.LOGIN
+	flow.auto_login = true
+	flow._auto_char_slot = 5
+	flow._selected_char_slot = -1
+	client.selects.clear()
+	client.char_list.emit([{"index": 0, "name": "Other"}])
+	_ck(client.selects.is_empty(), "absent explicit slot does not enter chars[0]")
+	flow._state = AppFlow.LOGIN
+	client.char_list.emit([{"index": 0, "name": "Other"}, {"index": 5, "name": "Fixture"}])
+	_ck(client.selects == [5] and flow._selected_char_slot == 5,
+			"explicit slot is entered and remembered for reconnect")
+
 	flow.queue_free()
 	await process_frame
 	if _fail == 0: