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/runtime/memory/store.go

@@ -246,6 +246,21 @@ func (s *Store) ListByPersona(ctx context.Context, personaID string) ([]MemoryIt
 	return scanItems(rows, "persona item")
 }
 
+// List returns every memory item, newest first, across all personas. It is the
+// aggregate/admin view that enumerates all persisted memory regardless of the
+// persona-isolation boundary; callers that must respect isolation should use
+// ListByPersona or ListScope instead. The returned slice is non-nil.
+func (s *Store) List(ctx context.Context) ([]MemoryItem, error) {
+	rows, err := s.db.QueryContext(ctx, `SELECT id, persona_id, role_id, project_id, scope, kind,
+		content, tags, confidence, source_conversation, created_at, updated_at,
+		decay_weight FROM memory_items
+		ORDER BY created_at DESC`)
+	if err != nil {
+		return nil, fmt.Errorf("memory: list items: %w", err)
+	}
+	return scanItems(rows, "item")
+}
+
 // scanItems reads every row into a MemoryItem slice, closing rows and wrapping
 // scan/iterate failures with the operation name. A non-nil, possibly empty slice
 // is always returned on success.