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/channelbridge/persist.go

@@ -0,0 +1,55 @@
+package channelbridge
+
+import (
+	"context"
+
+	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/history"
+)
+
+// This file holds the channelbridge's chat-history persistence hooks (design/16
+// §4.4): an owner private chat is routed INTO the single main web session and
+// tagged with the channel platform, then broadcast so the Web client mirrors it
+// without a refresh. Kept separate from channelbridge.go so the bridge's inbound
+// pipeline file stays under the module size bound.
+
+// SetOnPersisted wires (or replaces) the transport hook called after an
+// owner-private message is persisted into the main web session. The gateway is
+// built after the bridge in the composition root, so the hook is attached post-New
+// through this setter; it is a no-op-safe call and is safe for concurrent use with
+// in-flight processing.
+func (b *Bridge) SetOnPersisted(fn func(history.Message)) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	b.onPersisted = fn
+}
+
+// notifyPersisted hands a just-persisted message to the transport hook when one is
+// wired, so the gateway can broadcast `message_persisted` for cross-end sync.
+func (b *Bridge) notifyPersisted(msg history.Message) {
+	b.mu.RLock()
+	fn := b.onPersisted
+	b.mu.RUnlock()
+	if fn != nil {
+		fn(msg)
+	}
+}
+
+// persistToMain writes one message into the main web session with an explicit source
+// platform and client deviceID, then notifies the transport hook so Web clients receive
+// a `message_persisted` event without a refresh (design/16 §4.4). deviceID is the
+// concrete client that sent the message (design/16 §4.5) — e.g. "weixin-ilink:conf0:wx_uid"
+// for IM. It is a no-op when no history store is wired, so the bridge runs unchanged
+// without storage.
+func (b *Bridge) persistToMain(ctx context.Context, role, content, platform, deviceID string) {
+	if b.history == nil {
+		return
+	}
+	full, err := b.history.AppendFull(ctx, history.Message{
+		SessionID: history.MainSessionID, Role: role, Content: content, Platform: platform, DeviceID: deviceID,
+	})
+	if err != nil {
+		b.log.Warn("persist main session", "err", err, "role", role, "platform", platform, "device_id", deviceID)
+		return
+	}
+	b.notifyPersisted(full)
+}