docs: 整理文档目录结构 — 清理过时文档、归集功能子目录、统一命名规范

清理:
- 删除 34 份过时文档（gap reports/QA临时报告/验收报告/阶段性文档）
- 删除 docs/.hermes/skills 第三方 skills 副本（16 文件）
- 删除 skills-lock.json

目录归集:
- 根目录仅保留 README.md 索引
- product/ — 产品与架构设计（PRD + ARCHITECTURE + P2设计文档 + AI/企业路线图）
- tracking/ — Chatwoot parity 开发跟踪
- requirements/ — M01-M12 模块需求
- plans/ — 历史实现计划
- parity/ — 路由 parity 与前端契约
- qa/ — QA 报告与测试计划
- ops/ — 运维部署

命名规范:
- 全小写 kebab-case，禁止全大写文件名
- product/tracking/ops 用 NN- 序号前缀
- requirements 用 MNN- 两位零填充模块号
- plans/qa 用 YYYY-MM-DD- 日期前缀
- requirements M1-M9 零填充为 M01-M09（修复字典序）

同步更新:
- backend/cmd/route_parity/main.go 路径默认值
- backend/scripts/parity_frontend_smoke.sh 报告路径
- 所有 docs 内部交叉引用
- .gitignore 排除编译产物 (backend/gochat, backend/route_parity)
- 新增迁移 000052/000053
- 前端 WS 相关修改

backend/internal/handler/ws/protocol.go

@@ -22,6 +22,7 @@ const (
 	CommandSubscribe   CommandType = "subscribe"
 	CommandUnsubscribe CommandType = "unsubscribe"
 	CommandPing        CommandType = "ping"
+	CommandMessage     CommandType = "message" // client→channel action (e.g. update_presence)
 )
 
 // ServerMessageType — server→client message types
@@ -31,11 +32,11 @@ const (
 	// ServerEvent pushes a real-time event to subscribed clients
 	ServerEvent ServerMessageType = "event"
 	// ServerConfirmSubscribe acknowledges a successful subscription
-	ServerConfirmSubscribe ServerMessageType = "confirm_subscribe"
+	ServerConfirmSubscribe ServerMessageType = "confirm_subscription"
 	// ServerConfirmUnsubscribe acknowledges a successful unsubscribe
-	ServerConfirmUnsubscribe ServerMessageType = "confirm_unsubscribe"
+	ServerConfirmUnsubscribe ServerMessageType = "confirm_unsubscribe"  // NOTE: ActionCable uses confirm_subscription for both sub and unsub
 	// ServerRejectSubscribe rejects a subscription attempt
-	ServerRejectSubscribe ServerMessageType = "reject_subscribe"
+	ServerRejectSubscribe ServerMessageType = "reject_subscription"
 	// ServerPing is a heartbeat response
 	ServerPing ServerMessageType = "ping"
 	// ServerWelcome is sent immediately upon connection
@@ -66,6 +67,7 @@ type ChannelIdentifier struct {
 const (
 	ChannelAccount      = "AccountChannel"
 	ChannelConversation = "ConversationChannel"
+	ChannelRoom          = "RoomChannel" // Chatwoot single-subscription channel
 )
 
 // --- Server → Client Frames ---
@@ -158,5 +160,5 @@ const (
 
 const (
 	// PingInterval is how often the server sends ping frames to detect dead connections.
-	PingInterval = 30 // seconds
+	PingInterval = 5 // seconds — must be < ActionCable staleThreshold (6s) to avoid reconnect loops
 )