feat(backthink): 主动推送 sink 打通——hub.SendProactive + bridge.SendProactive + wire 接线

backthink 决策+路由(P2)就绪但无投递 sink(ActiveClient/IMAdapter 无实现)。补齐:
- gateway/proactive.go: hub.SendProactive 向 owner/admin 连接广播 proactive_message WS事件,
  内容脱敏(去RawData/media/token),返回接收数,count=0→IM兜底;Server.SendProactive 委托
- channelbridge/proactive.go: Bridge.SendProactive 解析 owner 账户(msg.Platform→匹配白名单账号,
  否则首个已配置主人频道),ChannelType=Direct+ChannelID/SenderID=owner id,走 adapter.SendProactive
- backthink/sinks.go: SetActiveSink/SetIMSink 晚注入(New后重建pusher,currentPusher 并发安全)
- wire.go: 在 gw/bridge 建好后 bt.SetActiveSink(gw)/SetIMSink(bridge)
- 投递链: think→parseProactive→ShouldPush→currentPusher.Push→gate→active(active_client)/IM(im_bridge)
  →record(route+送达数)
- 测试: sinks/gateway proactive/channelbridge proactive; 后端 build/vet/test 全绿
- 注: -race 本机 TSan 不可用(环境); 多平台IM按msg.Platform匹配 owner 账号(单sink诚实);
  weixin 24h窗口按 ErrProactiveWindow 记录为 im_bridge 错误不静默

internal/services/channelbridge/proactive.go

@@ -0,0 +1,100 @@
+package channelbridge
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	"git.yeij.top/AskaEth/Cyrene_v2/internal/channel/adapter"
+)
+
+// proactiveTarget is the owner's IM address (platform + account id) resolved for
+// a proactive push. The account id doubles as the DM peer on every adapter.
+type proactiveTarget struct {
+	platform  string
+	accountID string
+}
+
+// SendProactive pushes msg to the owner's IM channel via the registered adapter
+// for that platform. It is the backthink IMAdapter seam (design/12 §3 fallback).
+// The target account is chosen by msg.Platform when it names one of the owner's
+// whitelisted channels, otherwise the first whitelisted owner channel is used.
+// When the owner profile has no whitelisted account (or none carries an account
+// id) it returns a clear error so the caller records the reason rather than
+// silently dropping the push.
+func (b *Bridge) SendProactive(ctx context.Context, msg adapter.UnifiedMessage) error {
+	if err := ctx.Err(); err != nil {
+		return err
+	}
+	target, ok := b.proactiveTarget(msg)
+	if !ok {
+		return fmt.Errorf("channelbridge: no owner IM channel for proactive push")
+	}
+	ad := b.adapterForPlatform(target.platform)
+	if ad == nil {
+		return fmt.Errorf("channelbridge: no adapter for owner platform %q", target.platform)
+	}
+	out := msg
+	out.Platform = target.platform
+	out.ChannelType = adapter.ChannelDirect
+	// The owner's account id is the DM peer on every adapter: telegram/qq read
+	// ChannelID, kook/weixin read SenderID (with ChannelID as the fallback). Setting
+	// both keeps a direct message targetable regardless of which field the adapter
+	// prefers, without duplicating the message.
+	out.ChannelID = target.accountID
+	out.SenderID = target.accountID
+	if err := ad.SendProactive(ctx, out); err != nil {
+		return fmt.Errorf("channelbridge: send proactive via %q: %w", target.platform, err)
+	}
+	return nil
+}
+
+// proactiveTarget resolves the owner account a proactive push should reach:
+// msg.Platform, when it names one of the owner's whitelisted platforms, selects
+// that account; otherwise the first whitelisted owner channel (with a non-empty
+// account id) is used. A nil owner or an empty whitelist yields !ok.
+func (b *Bridge) proactiveTarget(msg adapter.UnifiedMessage) (proactiveTarget, bool) {
+	if b.owner == nil {
+		return proactiveTarget{}, false
+	}
+	accounts := b.owner.Accounts
+	if len(accounts) == 0 {
+		return proactiveTarget{}, false
+	}
+	platform := strings.ToLower(strings.TrimSpace(msg.Platform))
+	if platform != "" {
+		for _, acct := range accounts {
+			if acct.AccountID != "" && strings.EqualFold(acct.Platform, platform) {
+				return proactiveTarget{acct.Platform, acct.AccountID}, true
+			}
+		}
+	}
+	for _, acct := range accounts {
+		if acct.AccountID != "" {
+			return proactiveTarget{acct.Platform, acct.AccountID}, true
+		}
+	}
+	return proactiveTarget{}, false
+}
+
+// adapterForPlatform returns a registered adapter whose base platform matches
+// platform (multi-account names like "kook:3be..." resolve to their bare base),
+// preferring a connected one so a dead account is only tried when it is the only
+// option. It returns nil when none is registered.
+func (b *Bridge) adapterForPlatform(platform string) adapter.PlatformAdapter {
+	b.mu.RLock()
+	defer b.mu.RUnlock()
+	var first adapter.PlatformAdapter
+	for name, a := range b.adapters {
+		if !strings.EqualFold(basePlatform(name), platform) {
+			continue
+		}
+		if a.IsConnected() {
+			return a
+		}
+		if first == nil {
+			first = a
+		}
+	}
+	return first
+}