feat: IM平台列 + deviceID标识 + 会话持久化完善

- agent-96: chat_messages 加 platform 列(迁移0004) + IM主人私聊落主会话web(带platform) + 前端按平台过滤契约 + message_persisted 带 platform(复用 BroadcastPersisted)
- agent-97: chat_messages 加 device_id 列(迁移0005) + history.Message.DeviceID + Web发消息带deviceId(localStorage getClientId) + IM persistToMain 带 deviceID + 前端气泡展示 SourceLabel + 修主会话基础2个bug(fn scanMessage语法/DDL缺列)
- design/16 §4.4(平台) + §4.5(deviceID) 已入档
- 实机: POST /chat 带 deviceId 读回 user/assistant 均带 deviceId+platform; 后端 build/vet/test 绿 + 前端 build 绿
- 红线: 身份靠 actor 元数据; 禁止 shell 读 .env(JWT冒烟由主会话跑)

internal/services/gateway/session_persist.go

@@ -16,10 +16,11 @@ import (
 // persistUserMessages writes each RoleUser message of a submitted turn to the
 // history store so the raw user stream is durable before the turn resolves, then
 // notifies the transport so every browser of the same account can append it
-// without a manual refresh (design/16 §3.3, §4.2). It is a no-op when no history
-// store is wired. Rejected turns (empty, pending-full) never reach it, so nothing
-// vacuous is persisted.
-func (o *Orchestrator) persistUserMessages(ctx context.Context, sessionID string, messages []model.Message) {
+// without a manual refresh (design/16 §3.3, §4.2). deviceID tags the message with
+// the sending client (design/16 §4.5). It is a no-op when no history store is
+// wired. Rejected turns (empty, pending-full) never reach it, so nothing vacuous
+// is persisted.
+func (o *Orchestrator) persistUserMessages(ctx context.Context, sessionID string, messages []model.Message, deviceID string) {
 	if o.history == nil {
 		return
 	}
@@ -31,9 +32,9 @@ func (o *Orchestrator) persistUserMessages(ctx context.Context, sessionID string
 		if text == "" && image == "" {
 			continue
 		}
-		full, err := o.history.AppendFull(ctx, history.Message{SessionID: sessionID, Role: history.RoleUser, Content: text, Image: image})
+		full, err := o.history.AppendFull(ctx, history.Message{SessionID: sessionID, Role: history.RoleUser, Content: text, Image: image, DeviceID: deviceID})
 		if err != nil {
-			o.log.Error("orchestrator persist user", "err", err, "session", sessionID)
+			o.log.Error("orchestrator persist user", "err", err, "session", sessionID, "device_id", deviceID)
 			continue
 		}
 		o.notifyPersisted(full)
@@ -41,17 +42,18 @@ func (o *Orchestrator) persistUserMessages(ctx context.Context, sessionID string
 }
 
 // persistAssistantReply writes the final assistant text of a settled turn to the
-// history store, then notifies the transport (design/16 §3.3, §4.2). It is a
-// no-op when no history store is wired or the turn produced no text
-// (interrupted/errored turns leave res nil). The write runs under a fresh
-// background context so a canceled turn context never aborts it.
-func (o *Orchestrator) persistAssistantReply(sessionID string, res *loop.Result) {
+// history store, then notifies the transport (design/16 §3.3, §4.2). deviceID tags
+// the reply with the client that sent the turn (design/16 §4.5). It is a no-op
+// when no history store is wired or the turn produced no text (interrupted/errored
+// turns leave res nil). The write runs under a fresh background context so a
+// canceled turn context never aborts it.
+func (o *Orchestrator) persistAssistantReply(sessionID string, res *loop.Result, deviceID string) {
 	if o.history == nil || res == nil || res.Text == "" {
 		return
 	}
-	full, err := o.history.AppendFull(context.Background(), history.Message{SessionID: sessionID, Role: history.RoleAssistant, Content: res.Text})
+	full, err := o.history.AppendFull(context.Background(), history.Message{SessionID: sessionID, Role: history.RoleAssistant, Content: res.Text, DeviceID: deviceID})
 	if err != nil {
-		o.log.Error("orchestrator persist assistant", "err", err, "session", sessionID)
+		o.log.Error("orchestrator persist assistant", "err", err, "session", sessionID, "device_id", deviceID)
 		return
 	}
 	o.notifyPersisted(full)