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/hub.go

@@ -35,6 +35,7 @@ type Client struct {
 	Hub             *Hub              // reference back to Hub
 	SubscribedRooms map[string]bool   // rooms this client is subscribed to
 	CancelPresence  context.CancelFunc // cancel presence refresh on disconnect
+	Identifier      string            // ActionCable subscription identifier (JSON string)
 }
 
 // NewClient creates a new WebSocket client with the given identity and connection.
@@ -201,12 +202,9 @@ func (h *Hub) Register(c *Client) {
 	logger.L().Infof("ws hub: client registered (id=%s, user_id=%d, account_id=%d, is_contact=%v)",
 		c.ID, c.UserID, c.AccountID, c.IsContact)
 
-	// Send welcome message
-	welcomeMsg, _ := json.Marshal(wspkg.WSMessage{
-		Event: wspkg.EventWelcome,
-		Data:  map[string]any{"client_id": c.ID},
-	})
-	c.Send <- welcomeMsg
+	// Note: The ActionCable welcome frame is sent by handler.go's ServeWS
+	// after upgrade. We do NOT send a WSMessage-format welcome here because
+	// the JS ActionCable client only recognizes {type:"welcome"} frames.
 }
 
 // Unregister removes a client from the Hub and cleans up presence.
@@ -244,6 +242,37 @@ func (h *Hub) Unregister(c *Client) {
 	logger.L().Infof("ws hub: client unregistered (id=%s, user_id=%d)", c.ID, c.UserID)
 }
 
+
+// wrapActionCableMessage wraps a raw event payload in the ActionCable wire format.
+// ActionCable JS expects: {"identifier":"<subscription identifier>","message":<payload>}
+// Without the identifier field, the JS client crashes with
+// "Cannot read properties of undefined (reading 'received')".
+// Without the message field, the received callback gets undefined.
+//
+// If the client has no subscription identifier yet (pre-subscribe), the
+// message is still sent but without an identifier — the JS client will
+// silently ignore it (no matching subscription).
+func wrapActionCableMessage(identifier string, data []byte) []byte {
+	if identifier == "" {
+		// Client hasn't subscribed yet — sending an unwrapped message would
+		// crash the ActionCable JS client (no identifier to route to).
+		// Return nil to signal the caller to skip delivery.
+		return nil
+	}
+	wrapped := struct {
+		Identifier string          `json:"identifier"`
+		Message    json.RawMessage `json:"message"`
+	}{
+		Identifier: identifier,
+		Message:    data,
+	}
+	result, err := json.Marshal(wrapped)
+	if err != nil {
+		return data
+	}
+	return result
+}
+
 // SendToAccount sends a message to all clients subscribed to an account room.
 func (h *Hub) SendToAccount(accountID uint, data []byte) {
 	h.mu.RLock()
@@ -253,8 +282,12 @@ func (h *Hub) SendToAccount(accountID uint, data []byte) {
 	if clientIDs, ok := h.rooms[roomName]; ok {
 		for clientID := range clientIDs {
 			if client, ok := h.clients[clientID]; ok {
+				msg := wrapActionCableMessage(client.Identifier, data)
+				if msg == nil {
+					continue
+				}
 				select {
-				case client.Send <- data:
+				case client.Send <- msg:
 				default:
 					logger.L().Warnf("ws hub: dropping message for slow client %s", clientID)
 				}
@@ -273,8 +306,12 @@ func (h *Hub) SendToAccountConversation(accountID uint, conversationID uint, dat
 	if clientIDs, ok := h.rooms[roomName]; ok {
 		for clientID := range clientIDs {
 			if client, ok := h.clients[clientID]; ok {
+				msg := wrapActionCableMessage(client.Identifier, data)
+				if msg == nil {
+					continue
+				}
 				select {
-				case client.Send <- data:
+				case client.Send <- msg:
 				default:
 					logger.L().Warnf("ws hub: dropping message for slow client %s", clientID)
 				}
@@ -291,8 +328,12 @@ func (h *Hub) SendToRoom(room string, data []byte) {
 	if clientIDs, ok := h.rooms[room]; ok {
 		for clientID := range clientIDs {
 			if client, ok := h.clients[clientID]; ok {
+				msg := wrapActionCableMessage(client.Identifier, data)
+				if msg == nil {
+					continue
+				}
 				select {
-				case client.Send <- data:
+				case client.Send <- msg:
 				default:
 					logger.L().Warnf("ws hub: dropping message for slow client %s", clientID)
 				}
@@ -307,8 +348,12 @@ func (h *Hub) SendToClient(clientID string, data []byte) {
 	defer h.mu.RUnlock()
 
 	if client, ok := h.clients[clientID]; ok {
+		msg := wrapActionCableMessage(client.Identifier, data)
+		if msg == nil {
+			return
+		}
 		select {
-		case client.Send <- data:
+		case client.Send <- msg:
 		default:
 			logger.L().Warnf("ws hub: dropping message for slow client %s", clientID)
 		}