docs(gateway): WS 帧门相关 11 个文件的注释改中文（只改注释，代码零字节改动）

主人 2026-10-03 拍板「注释一律中文」。本次先把本会话动过的文件就地翻；
不做全仓一次性翻译，存量按包分批排期（见 工作小结.md 待办）。

范围：ws_frame_scope.go / ws_frame_scope_test.go / broadcast.go / ws_hub_turn.go /
ws_hub_message_event.go / session_read.go / server.go / ws_hub_stream_scope_test.go /
history_write_broadcast_test.go / mood_test.go / extra_test.go
含中文的整行注释 18 → 382。

校验（判据 = "只改注释、零代码字节改动"）：
- `git diff -U0 | 排除 +++/--- | 排除注释行/空行/行尾注释` → 为空
- 独立实现：两侧剥掉注释后逐行比对代码文本 → 11/11 文件全等，不一致数 0
- 行尾注释 7 行逐条列出，代码列与原文逐字节相同（gofmt 未要求重排）
- gofmt -l 干净；全树 go build/vet 绿；go test ./... = 58 包 ok / 0 FAIL；
  linux/amd64 + darwin/arm64 交叉编译绿
语义未删减：部分折行英文长句合并为更少行，故整行注释数 438 → 399。

internal/services/gateway/session_read.go

@@ -11,39 +11,36 @@ import (
 	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/history"
 )
 
-// This file owns the D4 read-cursor surface (Android collaboration B3): the
-// POST /api/v1/sessions/{id}/read endpoint that advances a session's read cursor,
-// plus the `session_read` realtime frame it broadcasts so the account's other
-// browsers clear the unread badge without a re-read. The cursor itself lives in
-// chat_sessions.read_at (internal/runtime/history); GET /sessions derives the
-// unreadCount from it (history.go). The cursor is session-scoped and single-owner:
-// one account, one cursor per session — reading on any one end marks the session
-// read for every end.
+// 本文件归属 D4 已读游标面（Android 协作 B3）：推进会话已读游标的
+// POST /api/v1/sessions/{id}/read 端点，以及它为清除账号其他浏览器
+// 未读徽标（无需重读）而广播的 `session_read` 实时帧。游标本身存于
+// chat_sessions.read_at（internal/runtime/history）；GET /sessions 由它
+// 推导 unreadCount（history.go）。游标是会话级、单所有者的：
+// 一个账号每个会话一个游标 —— 在任意一端阅读即为所有端标记该
+// 会话已读。
 
-// wsSessionRead is the WS event type for a read-cursor advance.
+// wsSessionRead 是已读游标推进的 WS 事件类型。
 const wsSessionRead = "session_read"
 
-// sessionReadRequest is the POST /api/v1/sessions/{id}/read body. Before is a
-// pointer so an absent field (an empty body) is distinguishable from an explicit
-// value: absent means "now" — the client marks everything it has seen read.
+// sessionReadRequest 是 POST /api/v1/sessions/{id}/read 的请求体。
+// Before 是指针，以便把字段缺失（空请求体）与显式取值区分开：
+// 缺失表示「现在」—— 客户端把它已看到的一切都标记为已读。
 type sessionReadRequest struct {
 	Before *int64 `json:"before"`
 }
 
-// handleMarkSessionRead advances a session's read cursor and answers
-// {data:{sessionId, readAt}} with the resulting cursor in Unix milliseconds.
-// It is owner/admin-gated like the other history writes (writeAuth).
+// handleMarkSessionRead 推进会话的已读游标，并以 Unix 毫秒返回结果
+// 游标 {data:{sessionId, readAt}}。与其他历史写入一样走 owner/admin
+// 门（writeAuth）。
 //
-// body {before?} is an optional millisecond timestamp bounding what is marked
-// read — messages with created_at <= readAt become read. Absent (or an empty body)
-// means now. A present non-positive or non-numeric before answers 400: the cursor
-// is a real millisecond timestamp, and "unread by a negative cursor" is not a
-// meaningful client request. An unknown session id answers 404; a missing
-// HistoryStore answers 501.
+// 请求体 {before?} 是可选毫秒时间戳，界定标记已读的范围 ——
+// created_at <= readAt 的消息变为已读。缺失（或空请求体）表示现在。
+// 已给出但非正数或非数值的 before 返回 400：游标是真实的毫秒
+// 时间戳，「负数游标造成的未读」不是有意义的客户端请求。未知
+// 会话 id 返回 404；HistoryStore 缺失返回 501。
 //
-// On success the new cursor is broadcast as a `session_read` frame so the account's
-// other browsers clear the badge too (reading on one end = read everywhere). A
-// failure path broadcasts nothing.
+// 成功时新游标作为 `session_read` 帧广播，使该账号其他浏览器也清除
+// 徽标（一端阅读 = 处处已读）。失败路径不广播任何东西。
 func (s *Server) handleMarkSessionRead(w http.ResponseWriter, r *http.Request) {
 	if s.history == nil {
 		writeError(w, &apperr.AppError{Code: "not_implemented", Message: "会话历史服务未配置（未注入 HistoryStore）", HTTPCode: http.StatusNotImplemented})
@@ -81,15 +78,13 @@ func (s *Server) handleMarkSessionRead(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusOK, map[string]any{"sessionId": id, "readAt": readAt})
 }
 
-// broadcastSessionRead fans a read-cursor advance out to every client as a
-// `session_read` frame carrying the session's new cursor, so the same account's
-// other ends clear the session's unread badge without a re-read. It is one of the
-// design/11 §7.1 「状态机信号」 (it reports a cursor, never a message body), so the
-// frame gate keeps it on the all-connections path. Like the other history frames it
-// relies on the hub having no per-session
-// subscription), and the client filters it by sessionId; the cursor's single source
-// of truth stays chat_sessions.read_at, so a client that missed the frame converges
-// on its next GET /sessions.
+// broadcastSessionRead 把一次已读游标推进作为 `session_read` 帧扇出到
+// 每个客户端，携带会话的新游标，使同一账号的其他端无需重读即可
+// 清除该会话的未读徽标。它属于 design/11 §7.1 的「状态机信号」
+// （只报告游标，绝不报告消息正文），因此帧门让它留在全连接路径上。
+// 与其他历史帧一样，它依赖 hub 没有按会话订阅这一点，由客户端按
+// sessionId 过滤；游标的唯一事实来源仍是 chat_sessions.read_at，
+// 因此错过该帧的客户端会在下次 GET /sessions 时重新收敛。
 func (h *hub) broadcastSessionRead(sessionID string, readAt int64) {
 	h.broadcast(wsEvent{
 		Type:      wsSessionRead,