feat(gateway,security): WS 下行帧角色门 — 内容帧仅 owner+admin，viewer 只收状态机信号

design/11 §7.1（主人 2026-10-03 拍板）。此前 hub.broadcast 是全连接广播，而任意角色
（含 viewer）都能连 /ws/chat ⇒ viewer 能收到角色回复正文（message.*）、推理内容
（thinking.*）、消息增量、graph_update、mood 等。这与 design/19 §1/§3「flow 可视化仅
owner/admin 可见」冲突，也与 GET /sessions/{id}/messages 的 owner/admin 档位不一致。

收口：唯一分类点 internal/services/gateway/ws_frame_scope.go 的 frameReachesAll(typ)
（fail-closed switch，默认 false）；hub.broadcast 投递前查表，白名单外对非 owner/admin
连接直接跳过。**不给 broadcast 加 bool 参数、不让调用点自己判断** —— 那正是"漏一处就是
泄漏"的形状。全包只有一个 fan-out 循环，14 个 .broadcast( 调用点全部落进该入口。

- 白名单只有 7 个状态机信号帧（不含任何内容）：session_busy / pending_ack / pending_drain /
  session_idle / session_interrupted / pending_full / session_read
- 其余全部（流式 message/thinking/tool_call、message_persisted/edited/deleted、graph_update、
  subagent_event/result、task_output/task_done、automation_result、tool_used、capacity_awaken、
  mode_switch、mood、device_update、reminder）仅 owner+admin
- 语义澄清：本门管「谁被主动推送」，数据可见性仍由 REST 决定（viewer 的 12 条只读监控端点
  不变，含 GET /personas 的 mood）；/ws/chat 连接鉴权与 voice_output 定向帧不动

契约：Docs/api-client.md → v0.48（对 viewer 是收紧；owner/admin 零变化；无端点/字段形状变更）

验证：go build/vet 绿；go test ./... = 58 包 ok / 0 FAIL；-race ./internal/services/gateway/... ok；
linux/amd64 + darwin/arm64 交叉编译绿。真 httptest WS + 真 JWT 按角色逐帧实测 37 帧：
viewer 只收到 7 个状态信号，owner/admin 37/37。
变异验证：① graph_update 加回白名单 → 真 WS 抓到 viewer 收到 graph_update，3 个测试 FAIL；
② session_idle 移出白名单 → 3 个测试 FAIL（viewer 等不到哨兵帧而超时）。均已还原。

遗留（已登记，待主人裁决）：① 握手 history 回放对任意角色照发（viewer 连上即得主会话最近
50 条正文）；② /ws/chat 上行未按角色授权（viewer 可发 chat = 真驱动模型并落库；
subagent_ask / task_output_query 的定向应答绕过本门）。

internal/services/gateway/ws_hub.go

@@ -48,7 +48,8 @@ type wsInbound struct {
 	Data  json.RawMessage `json:"data,omitempty"`
 }
 
-// hub owns the connection set and relays bus events to every client.
+// hub owns the connection set and relays bus events to clients, each frame
+// gated by its type (see broadcast / ws_frame_scope.go).
 type hub struct {
 	mu           sync.RWMutex
 	conns        map[*wsConn]struct{}
@@ -157,17 +158,30 @@ func (h *hub) connCount() int {
 	return len(h.conns)
 }
 
-// broadcast fans an event out to every registered connection without blocking on
-// any single (possibly slow) client: a full send buffer drops the frame.
+// broadcast is the single delivery entry for outbound frames, and the design/11
+// §7.1 role gate itself: it looks the frame's type up (frameReachesAll) and fans
+// a registered 「状态机信号」 out to every registered connection, while every other
+// type — content, tool, persisted-message, graph, private-state, and any type not
+// classified yet — reaches owner + admin only. Registration happens only after the
+// JWT is verified (ws_hub_conn.go), so the connection set is the authenticated set.
+//
+// Gating here rather than at the call sites is deliberate: there is exactly one
+// fan-out loop, so a frame cannot be sent to the wrong audience by a call site that
+// forgot to pick the restricted entry. It never blocks on any single (possibly
+// slow) client: a full send buffer drops the frame.
 func (h *hub) broadcast(ev wsEvent) {
 	b, err := json.Marshal(ev)
 	if err != nil {
 		h.log.Warn("marshal broadcast", "err", err)
 		return
 	}
+	adminOnly := !frameReachesAll(ev.Type)
 	h.mu.RLock()
 	defer h.mu.RUnlock()
 	for c := range h.conns {
+		if adminOnly && !ownerAdminClaims(c.claims) {
+			continue
+		}
 		c.enqueue(b)
 	}
 }