feat(gateway): admin 列表端点接真实数据——persona/session/memory 补 List() 并注入 gateway.Deps

根因：gateway.Server 定义 SessionStore/PersonaStore/MemoryStore 接口但生产从未满足：
- 底层 manager 无 List() 方法；
- wireFrontend 的 gateway.Deps{} 未传 Session/Personas/Memories。
→ /api/v1/sessions|personas 与 /api/v1/admin/{sessions,personas,memories} 恒返回 []。

改动：
- persona/registry：Registry.List() []Character（并发安全、值拷贝）。
- channel/session：SessionManager.List(ctx)（查 channel_sessions 表+按 actor_role 重建）。
- runtime/memory：Store.List(ctx)（全表，复用 scanItems）。
- gateway 三 Store 接口改为返回域类型（Character/MemoryItem），映射统一放 collect* 侧。
- cmd/cyrene/wire.go：Deps 补传 Session/Personas/Memories。
- .gitignore：cyrene→/cyrene（锚定根，不再误伤 cmd/cyrene 目录）。

实机验证：/api/v1/admin/personas 返回 {id:cyrene,name:昔涟,isDefault:true}。

internal/channel/session/manager.go

@@ -5,6 +5,7 @@ import (
 	"database/sql"
 	"fmt"
 	"log/slog"
+	"strings"
 	"sync"
 	"time"
 
@@ -40,6 +41,18 @@ VALUES (?, ?, ?, ?, ?, ?)`
 const selectSessionSQL = `
 SELECT session_id FROM channel_sessions WHERE platform = ? AND channel_id = ?`
 
+// listSessionsSQL selects every persisted channel mapping, newest first. Group
+// sessions key on a channel_id carrying groupChannelPrefix; direct sessions use
+// their channel id.
+const listSessionSQL = `
+SELECT platform, channel_id, session_id, actor_role FROM channel_sessions
+ORDER BY created_at DESC`
+
+// groupChannelPrefix marks a channel id as a group conversation so a session
+// reconstructed from the backing table (where no IsGroup flag is persisted) can
+// still report group membership.
+const groupChannelPrefix = "group:"
+
 // SessionManager owns the channel↔session mapping. It backs the map with the
 // SQLite table channel_sessions so a channel keeps its internal session across
 // restarts, and it caches lookups in memory to avoid a query per message. The
@@ -109,6 +122,49 @@ func (m *SessionManager) GetOrCreate(ctx context.Context, msg adapter.UnifiedMes
 	return s, nil
 }
 
+// List returns every known session, newest first, across the backing table and
+// the in-memory cache. Rows that are still in the cache are returned with their
+// full derived metadata (Owner/IsGroup/MemWritable from the original resolve);
+// rows recovered from the table (for example from a previous process) are
+// reconstructed from the persisted actor role. The returned slice is non-nil. It
+// is safe for concurrent use.
+func (m *SessionManager) List(ctx context.Context) ([]Session, error) {
+	rows, err := m.db.QueryContext(ctx, listSessionSQL)
+	if err != nil {
+		return nil, fmt.Errorf("session: list: %w", err)
+	}
+	defer func() { _ = rows.Close() }()
+
+	sessions := make([]Session, 0)
+	for rows.Next() {
+		var platform, cid, sessionID, roleStr string
+		if err := rows.Scan(&platform, &cid, &sessionID, &roleStr); err != nil {
+			return nil, fmt.Errorf("session: scan list: %w", err)
+		}
+		key := platform + "\x00" + cid
+		if cached, ok := m.lookupCached(key); ok {
+			sessions = append(sessions, cached)
+			continue
+		}
+		role := adapter.Role(roleStr)
+		owner := role == adapter.RoleOwner
+		isGroup := strings.HasPrefix(cid, groupChannelPrefix)
+		sessions = append(sessions, Session{
+			Platform:    platform,
+			ChannelID:   cid,
+			SessionID:   sessionID,
+			ActorRole:   role,
+			Owner:       owner,
+			IsGroup:     isGroup,
+			MemWritable: owner && !isGroup,
+		})
+	}
+	if err := rows.Err(); err != nil {
+		return nil, fmt.Errorf("session: iterate list: %w", err)
+	}
+	return sessions, nil
+}
+
 // lookupCached returns the cached session for key under a read lock.
 func (m *SessionManager) lookupCached(key string) (Session, bool) {
 	m.mu.RLock()
@@ -144,7 +200,7 @@ func (m *SessionManager) persist(ctx context.Context, platform, cid string, acto
 func channelID(msg adapter.UnifiedMessage) string {
 	if msg.IsGroup() {
 		if msg.GroupID != "" {
-			return "group:" + msg.GroupID
+			return groupChannelPrefix + msg.GroupID
 		}
 		return msg.ChannelID
 	}