feat(space): 共享工作区增量3a —— Agent 编排按 Space 共享(纯 PG 打样)

引入 Space 中间容器(租户>Space>成员),资源作用域从 owner 改为 space_id，
让"个人私有/项目临时组队/整租户共享"出自同一模型(设计见 SPACE_DESIGN.md)。
先在纯 PG 的 Agent 上打样，零存储风险，验证协作+RBAC+切换 UX。

后端:
- 新表 Space{tenant_id,name,kind,creator,archived} + SpaceMember{space_id,user_id,role}
  (如 Tenant 般不 isTenantScoped)；User.ActiveSpaceID；Agent 作用域 owner→space_id，
  owner 降级为创建人(供 UI 显示 / 删他人鉴权)
- store/space.go:个人空间幂等/活跃空间解析/切换/列表/建/成员CRUD/归档
- 迁移顺序坑:结构体只放非唯一 index，MigrateAgentSpaces 回填 space_id 后再建唯一
  索引 idx_agent_sn + DROP 旧 idx_agent_on(否则存量空 space_id 撞车)；启动序4步幂等
- 中间件 SpaceContext(注入 space_id) + RequireSpaceRole(照 RequireTenantRole)
- handler/space.go 空间端点 + 路由；agent.go 改空间作用域(删/覆盖他人需 admin)
- 计费零改动(Space 与 ResolveBillingTenantID 正交)

桌面端:
- api.ts space 接口；顶栏 SpaceSwitcher(含新建项目空间)；StudioView 随空间切换
  重拉编排 + viewer 禁保存；Agent 列表显示创建人 + 按 mine 控删除

验证:中间件6门控单测 + DB迁移(13个人空间/9 Agent全re-key/索引换新) + 后端HTTP全
场景(member见他人编排/删他人403、viewer存403、非成员切空间400+隔离、owner删他人200)
+ 浏览器实机(切换器3空间/Studio空间编排随切换隔离刷新/创建人显示/console无错)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

sundynix-gateway/internal/middleware/space_role_test.go

@@ -0,0 +1,60 @@
+package middleware
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+
+	"github.com/sundynix/sundynix-gateway/internal/store"
+)
+
+type fakeSpaceRole struct{ role string }
+
+func (f fakeSpaceRole) SpaceMemberRole(context.Context, string, string) string { return f.role }
+
+func spaceGateEngine(uid, space, memberRole, minRole string) *gin.Engine {
+	gin.SetMode(gin.TestMode)
+	r := gin.New()
+	r.Use(func(c *gin.Context) {
+		if uid != "" {
+			c.Set(CtxUserID, uid)
+		}
+		if space != "" {
+			c.Set(CtxSpaceID, space)
+		}
+		c.Next()
+	})
+	r.POST("/agents", RequireSpaceRole(fakeSpaceRole{role: memberRole}, minRole),
+		func(c *gin.Context) { c.String(http.StatusOK, "saved") })
+	return r
+}
+
+func TestRequireSpaceRole_Gate(t *testing.T) {
+	cases := []struct {
+		name       string
+		uid        string
+		space      string
+		memberRole string
+		wantCode   int
+	}{
+		{"owner 放行", "u1", "s1", store.RoleOwner, http.StatusOK},
+		{"admin 放行", "u1", "s1", store.RoleAdmin, http.StatusOK},
+		{"member 放行", "u1", "s1", store.RoleMember, http.StatusOK},
+		{"viewer 拦下(空间只读)", "u1", "s1", store.RoleViewer, http.StatusForbidden},
+		{"非空间成员 拦下", "u1", "s1", "", http.StatusForbidden},
+		{"未登录 401", "", "s1", store.RoleOwner, http.StatusUnauthorized},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			r := spaceGateEngine(tc.uid, tc.space, tc.memberRole, store.RoleMember)
+			w := httptest.NewRecorder()
+			r.ServeHTTP(w, httptest.NewRequest(http.MethodPost, "/agents", nil))
+			if w.Code != tc.wantCode {
+				t.Errorf("状态码=%d, 期望 %d（body=%s）", w.Code, tc.wantCode, w.Body.String())
+			}
+		})
+	}
+}