feat(session,runtime): 多角色并存—按会话选角（迁移0011 + 按回合解析 + agent池 + 提取器修正）

按 DevDocs/design/22 批次 1 后端（§2/§3/§4.1-4.5/§4.7/§5 验收 1-6）。
- 迁移 0011：chat_sessions.persona_id + chat_messages.persona_id（均 DEFAULT ''，无回填 → 升级零风险）；同步包内幂等 DDL；**真实库升级验证**（拷贝 data/cyrene.db 到临时目录跑 MigrateUp：既有 1 会话/109 消息 persona 仍为 ''，原库未被触碰）
- history：SessionMeta/Message 加 PersonaID + SetSessionPersona；ListSessions/List/scan/Append 带上
- runtime：SessionEnv.PersonaID + loop.personaFor(ctx) 替换固定 l.personaID（memory/request/turn）+ **agent 池**（Options.Agents，按角色取 instructions，未命中回落）+ **提取器不再把 persona 烤死在构造期**（多角色下记忆不再永远记在 cyrene 名下）+ **thinking 旋钮改为按会话角色解析**（否则角色 Y 会用角色 X 的预算/展示）
- gateway：会话 DTO/POST/PATCH 支持 personaId；ws/rest/voice 的 OwnerEnv 硬编改为**按会话解析角色**（actor 元数据语义不变）；admin memories 搜索去掉硬编 cyrene
- Docs/api-client v0.42；**两处有意的行为收紧**已写明：POST /sessions body 非法 JSON → 400（原先完全忽略 body；空/null/{} 仍 201）；POST /admin/memories/search 省略 personaId 且无默认角色 → 400（原先默认查 cyrene）
- 测试：design/22 §5 验收 1-6（记忆隔离/提示词首条 system/情绪按角色/提取 persona 归属/迁移兼容）+ 进程内 e2e（断言 adapter 收到的 model.Request.Messages[0] 即该角色的 systemPrompt）
- **已知未做（留批次 2 / 待确认）**：① IM 与渠道级未做 → **§7-3「owner 私聊镜像随主会话角色」尚未生效**；② 请求级覆盖未实现（本批只做会话级）；③ **§7-5 的「上下文发送角色标记」只完成存储+DTO 半边**——消息 persona 已落库且 DTO 已带，但模型上下文不从 chat_messages 重建，「第 N 条是谁说的」尚未进上下文（需确认是否属批次 2）；④「切角色重建摘要」当前是空操作（压缩未接线）；⑤ thinking 旋钮仅在流式路径生效（非流式 agent.RunStep 不带，A 批次既有性质）
- 验收：go build/vet/test 全绿 + linux/amd64 与 darwin/arm64 交叉编译（既有 flake 本轮未触发；同批 session_orchestrator.go 一度 501 行 → 抽出 session_tail.go）

internal/runtime/loop/memory.go

@@ -36,11 +36,12 @@ type asyncExtractor interface {
 // project memory is injected so no owner-sensitive memory leaks to a group or
 // stranger.
 func (l *Loop) injectMemory(ctx context.Context, messages []model.Message) []model.Message {
-	if l.retriever == nil || l.personaID == "" {
+	personaID := l.personaFor(ctx)
+	if l.retriever == nil || personaID == "" {
 		return messages
 	}
 	env := sessionEnvFrom(ctx)
-	block, err := l.retrieveMemoryBlock(ctx, env, queryFromMessages(messages))
+	block, err := l.retrieveMemoryBlock(ctx, env, personaID, queryFromMessages(messages))
 	if err != nil {
 		l.log.Warn("memory inject", "error", err, "env", env.ActorEnv)
 		return messages
@@ -54,16 +55,16 @@ func (l *Loop) injectMemory(ctx context.Context, messages []model.Message) []mod
 	return out
 }
 
-// retrieveMemoryBlock returns the memory injection block for env. The owner-full
-// env keeps the pre-existing Inject behavior. The restricted env (group chat /
-// stranger) injects only project-scope memory (人人可读, not owner-private) and
-// marks the block as group-isolated so callers can tell an isolated read from the
-// owner's full read.
-func (l *Loop) retrieveMemoryBlock(ctx context.Context, env SessionEnv, query string) (string, error) {
+// retrieveMemoryBlock returns the memory injection block for env and the turn's
+// role. The owner-full env keeps the pre-existing Inject behavior. The restricted
+// env (group chat / stranger) injects only project-scope memory (人人可读, not
+// owner-private) and marks the block as group-isolated so callers can tell an
+// isolated read from the owner's full read.
+func (l *Loop) retrieveMemoryBlock(ctx context.Context, env SessionEnv, personaID, query string) (string, error) {
 	if !env.Restricted() {
-		return l.retriever.Inject(ctx, l.personaID, query, 0)
+		return l.retriever.Inject(ctx, personaID, query, 0)
 	}
-	results, err := l.retriever.Retrieve(ctx, l.personaID, query, 0)
+	results, err := l.retriever.Retrieve(ctx, personaID, query, 0)
 	if err != nil {
 		return "", err
 	}
@@ -228,13 +229,18 @@ func (l *Loop) extractMemoryAsync(ctx context.Context, messages []model.Message,
 	}()
 }
 
-// persistMemories writes extracted items to the memory store, scoping any item
-// the extractor left unscoped to the loop's persona. Store failures are logged
-// and never fatal, so one rejected item cannot abort a turn.
+// persistMemories writes extracted items to the memory store, stamping every item
+// with the role that produced the turn. The assignment is unconditional on
+// purpose: the extractor is deliberately role-agnostic (it no longer holds a
+// persona baked in at construction, cmd/cyrene/extractor.go), so a multi-role
+// process would otherwise file every memory under one role. A blank role (no
+// persona configured at all) leaves the item as the extractor produced it. Store
+// failures are logged and never fatal, so one rejected item cannot abort a turn.
 func (l *Loop) persistMemories(ctx context.Context, items []memory.MemoryItem, step int) {
+	personaID := l.personaFor(ctx)
 	for _, it := range items {
-		if it.PersonaID == "" && l.personaID != "" {
-			it.PersonaID = l.personaID
+		if personaID != "" {
+			it.PersonaID = personaID
 		}
 		if _, err := l.memory.Add(ctx, it); err != nil {
 			l.log.Warn("memory store", "step", step, "error", err)