feat: 公共平台最小化打扰(design/12 §6)——5条策略: 分级+轻思考+限流+审查剔噪

降噪A(策略一/二/五):
- channelbridge/light.go: 非owner分级门——小事件当系统消息登记(不进loop)、非owner轻响应(她判断回/不回,规则优先mention/关键词+轻LLM兜底fail-closed静默)
- backthink 触发降噪: SubjectSystemEvent 低价值不唤醒thinking(仅高价值/owner才think), iot/reminder不受影响
- quiet hours: 安静时段非owner无信号静默,被@才回(非硬性静默); config QUIET_START/END_HOUR 单源共用

限流B(策略三/四):
- adapter/flowgate.go: per-adapter 滑窗限流器+总上限+审查剔噪闸门(Admit两连:速率+上限/审查), owner私聊绕过
- channelbridge/flowgate.go: onMessage入站最前挂闸, 超限/被剔不占worker槽; 审查模型NewLLMReviewer复用model.Adapter(仅>80%阈值触发+跨分钟节流,失败回退FIFO,绝不判身份)
- config: ChannelAccount 加 GroupMsgPerMin(默认6)/MsgPerMin/MaxMessages(默认50), CHANNELS_JSON每账号, 向后兼容
- 被剔消息走OnRejected审计不静默丢

main wire接线: 加modelAdapter字段+Review注入(reviewFor nil-safe,无LLM回退FIFO)
全仓 go build/vet/test 绿(53包)+交叉编译, 零新依赖, 前端无涉

internal/config/channels_test.go

@@ -53,6 +53,39 @@ func TestParseChannelAccounts_MultiAccountWithAllowDeny(t *testing.T) {
 	}
 }
 
+func TestParseChannelAccounts_FlowLimitFields(t *testing.T) {
+	t.Parallel()
+	raw := `{
+		"telegram": [
+			{"id":"conf0","config":{"bot_token":"t0"},"groupMsgPerMin":10,"maxMessages":80,"msgPerMin":30}
+		]
+	}`
+	got, err := ParseChannelAccounts(raw)
+	if err != nil {
+		t.Fatalf("ParseChannelAccounts: %v", err)
+	}
+	a := got["telegram"][0]
+	if a.GroupMsgPerMin != 10 || a.MsgPerMin != 30 || a.MaxMessages != 80 {
+		t.Fatalf("flow fields = group:%d msg:%d max:%d, want 10/30/80",
+			a.GroupMsgPerMin, a.MsgPerMin, a.MaxMessages)
+	}
+}
+
+func TestParseChannelAccounts_NoFlowFieldsDefaultsToZero(t *testing.T) {
+	t.Parallel()
+	raw := `{"telegram":[{"id":"conf0","config":{"bot_token":"t0"}}]}`
+	got, err := ParseChannelAccounts(raw)
+	if err != nil {
+		t.Fatalf("ParseChannelAccounts: %v", err)
+	}
+	a := got["telegram"][0]
+	// Absent fields stay zero; the bridge maps zero to the protective defaults
+	// (6 group/min, 50 max), so old accounts are backward compatible.
+	if a.GroupMsgPerMin != 0 || a.MsgPerMin != 0 || a.MaxMessages != 0 {
+		t.Fatalf("absent flow fields should be zero, got %+v", a)
+	}
+}
+
 func TestParseChannelAccounts_Malformed(t *testing.T) {
 	t.Parallel()
 	if _, err := ParseChannelAccounts(`{`); err == nil {