feat(channel,runtime): 批次2 后端 — 消息级角色归属进上下文 + IM 私聊随主会话角色 + 渠道级绑定

按 design/22 §2/§3/§4.4/§7（3/4/5）。
- ①「消息级角色归属」进入模型上下文（批次 1 只做存储+DTO）：历史消息的发送角色现在对模型可见，且**不把系统元数据塞进用户正文**（design/11 §10 红线）
- ② IM owner 私聊镜像解析出的角色 = **主会话绑定的角色**（§7-3）
- ③ 渠道级绑定：ChannelAccount 加 personaId（channels.json 读写/校验/脱敏沿用既有约定）+ 角色解析优先级 **会话 > 渠道 > 默认** + **群聊/陌生人强制默认角色**（§7-4）；admin 渠道配置端点支持 personaId
- Docs/api-client 版本 +1
- 验收：go build/vet/test 全绿 + linux/darwin 交叉编译

internal/services/gateway/session_attribution_test.go

@@ -0,0 +1,139 @@
+package gateway
+
+import (
+	"context"
+	"net/http"
+	"strings"
+	"testing"
+
+	"git.yeij.top/AskaEth/Cyrene_v2/internal/auth"
+	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/agent"
+	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/history"
+	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/loop"
+	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/model"
+)
+
+// This file covers the end-to-end half of design/22 §7-5: a session that switched
+// roles must keep the conversation it had, and the model must be able to tell
+// which utterances came from the earlier role. The chain asserted here is:
+// chat_messages (per-message persona_id) → the orchestrator's seeded turn context
+// → the loop's speaker attribution → the model.Request the adapter receives.
+
+// requestTexts returns the text of every message of req, in order.
+func requestTexts(req model.Request) []string {
+	out := make([]string, 0, len(req.Messages))
+	for _, m := range req.Messages {
+		out = append(out, messageTextOf(m))
+	}
+	return out
+}
+
+// messageTextOf concatenates the text parts of m.
+func messageTextOf(m model.Message) string {
+	var b strings.Builder
+	for _, c := range m.Content {
+		if c.Type == model.ContentTypeText {
+			b.WriteString(c.Text)
+		}
+	}
+	return b.String()
+}
+
+// TestChatTurnCarriesSpeakerAttributionFromTranscript is design/22 §7-5 accepted
+// from the process boundary: the session already holds turns spoken by role X, it
+// is now bound to role Y, and one more chat turn arrives. The request must carry
+// X's earlier utterance with its speaker attributed to X (not to Y), keep every
+// stored body verbatim, and still open with Y's own instructions.
+func TestChatTurnCarriesSpeakerAttributionFromTranscript(t *testing.T) {
+	t.Parallel()
+	ctx := context.Background()
+	st := personaTestStore(t)
+	reg := personaTestRegistry(t)
+	sub, err := st.NewSubSessionFor(ctx, "owner", "yuki")
+	if err != nil {
+		t.Fatalf("NewSubSessionFor: %v", err)
+	}
+	// The conversation as it stood while the session spoke as X, with per-message
+	// persona ids exactly as the orchestrator persists them (design/22 §7-5).
+	for _, m := range []history.Message{
+		{SessionID: sub, Role: history.RoleUser, Content: "你还记得吗", PersonaID: "xilian", CreatedAt: 1000},
+		{SessionID: sub, Role: history.RoleAssistant, Content: "我记住了，你喜欢冰美式", PersonaID: "xilian", CreatedAt: 1001},
+	} {
+		if err := st.Append(ctx, m); err != nil {
+			t.Fatalf("seed transcript: %v", err)
+		}
+	}
+
+	ad := &personaAdapter{}
+	xilian := gatewayAgentFor(t, "你是昔涟。", ad)
+	yuki := gatewayAgentFor(t, "你是由纪。", ad)
+	names := map[string]string{"xilian": "昔涟", "yuki": "由纪"}
+	l := loop.New(loop.Options{
+		Agent:       xilian,
+		Agents:      map[string]*agent.Agent{"xilian": xilian, "yuki": yuki},
+		PersonaID:   "xilian",
+		PersonaName: func(id string) string { return names[id] },
+	})
+	_, ts, jwt := buildEnv(t, cfgDefault(), Deps{History: st, Personas: reg, Loop: l})
+	tok := signAny(t, jwt, "acct", auth.RoleOwner)
+
+	resp, body := doReq(t, http.MethodPost, ts.URL+"/api/v1/chat", map[string]any{"sessionId": sub, "text": "继续"}, tok)
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("chat status = %d, want 200 (body=%s)", resp.StatusCode, body)
+	}
+	if len(ad.reqs) == 0 {
+		t.Fatal("the model adapter saw no request")
+	}
+	req := ad.reqs[len(ad.reqs)-1]
+
+	// The answering role still owns the head of the prompt.
+	if got := firstSystemText(req); got != "你是由纪。" {
+		t.Fatalf("first system = %q, want role Y's prompt", got)
+	}
+
+	// X's earlier utterance reached the model, verbatim (the turn is not amnesiac
+	// across the role switch).
+	texts := requestTexts(req)
+	xIdx := -1
+	for i, txt := range texts {
+		if txt == "我记住了，你喜欢冰美式" {
+			xIdx = i
+			break
+		}
+	}
+	if xIdx < 0 {
+		t.Fatalf("X's earlier utterance missing from the request: %q", texts)
+	}
+	if xIdx == 0 || req.Messages[xIdx].Role == model.RoleSystem {
+		t.Fatalf("X's utterance must stay a plain assistant message, got %+v", req.Messages[xIdx])
+	}
+	if req.Messages[xIdx].SenderName != "xilian" {
+		t.Fatalf("speaker label = %q, want xilian (the role that actually spoke it)", req.Messages[xIdx].SenderName)
+	}
+
+	// The speaker boundary names X and marks the stretch as not Y's own words.
+	note := ""
+	for _, m := range req.Messages {
+		if m.Role == model.RoleSystem && strings.Contains(messageTextOf(m), "「昔涟」（xilian）") {
+			note = messageTextOf(m)
+			break
+		}
+	}
+	if note == "" || !strings.Contains(note, "不是你说的") {
+		t.Fatalf("no speaker boundary for X found: %q", texts)
+	}
+
+	// No stored body was rewritten, and the newly sent user text carries no system
+	// metadata (the user lane stays free text, design/11 §10).
+	for _, m := range req.Messages {
+		if m.Role != model.RoleUser {
+			continue
+		}
+		if txt := messageTextOf(m); txt != "继续" && txt != "你还记得吗" {
+			t.Fatalf("user body = %q, want a stored/verbatim user text", txt)
+		}
+	}
+	if xIdx+1 <= len(req.Messages) && strings.Contains(req.Messages[xIdx].Content[0].Text, "[") {
+		t.Fatalf("attribution leaked into X's body: %q", req.Messages[xIdx].Content[0].Text)
+	}
+}