feat(desktop): 顶栏租户切换器（多租户）—— 切换活跃租户即换工作区+计费

用户属多个租户时，顶栏显示租户下拉（Building2 图标）：切换即调 POST /me/tenant
换活跃租户，随后刷新余额芯片（显示新计费租户的可花余额）。仅 >1 租户时出现。
api 加 myTenants/switchTenant。

live 验证(preview)：demoB(属公司A+公司B) 切换器显两租户；从公司A(共享,余额15.84)
切到公司B(个人,余额6.38)→ 后端 active 持久化、芯片随之更新为 6.4(橙,偏低)。tsc+48 测试全过。

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

sundynix-desktop/frontend/src/App.tsx

@@ -15,7 +15,7 @@ import { Placeholder } from "./views/Placeholder";
 import { CommandPalette, type Command } from "./components/CommandPalette";
 import { UpdateBanner } from "./components/UpdateBanner";
 import { Login } from "./views/Login";
-import { submitTask, streamTokens, streamExec, taskStatus, listRuns, authMe, logout, tenantCurrent, type Identity, type AuthUser, type TenantCtx } from "./lib/api";
+import { submitTask, streamTokens, streamExec, taskStatus, listRuns, authMe, logout, tenantCurrent, myTenants, switchTenant, type Identity, type AuthUser, type TenantCtx, type MyTenant } from "./lib/api";
 import type { TaskDsl } from "./lib/dsl";
 import { emptyRun, type RunState } from "./lib/run";
 import { ToastProvider } from "./ui";
@@ -43,6 +43,7 @@ export default function App() {
   const [view, setView] = useState<ViewKey>("home");
   const [user, setUser] = useState<AuthUser | null>(null);
   const [tenant, setTenant] = useState<TenantCtx | null>(null);
+  const [tenants, setTenants] = useState<MyTenant[]>([]);
   const [authLoading, setAuthLoading] = useState(true);
   const identity = useMemo<Identity>(() => ({ userId: user?.id ?? "", sessionId: getSessionId() }), [user]);
   const [run, setRun] = useState<RunState>(emptyRun);
@@ -92,10 +93,25 @@ export default function App() {
     tenantCurrent()
       .then(setTenant)
       .catch(() => {});
+    myTenants()
+      .then((r) => setTenants(r.tenants))
+      .catch(() => {});
   }, []);
+  const onSwitchTenant = useCallback(
+    async (id: string) => {
+      try {
+        await switchTenant(id);
+        refreshTenant();
+      } catch {
+        /* ignore */
+      }
+    },
+    [refreshTenant],
+  );
   useEffect(() => {
     if (!user) {
       setTenant(null);
+      setTenants([]);
       return;
     }
     refreshTenant();
@@ -239,7 +255,7 @@ export default function App() {
         style={{ background: "radial-gradient(60% 100% at 50% 0%, rgba(124,92,246,0.10), transparent 70%)" }}
       />
       <UpdateBanner />
-      <TopBar user={user} tenant={tenant} onLogout={onLogout} onCommand={() => setCmdOpen(true)} onOpenUsage={() => setView("usage")} />
+      <TopBar user={user} tenant={tenant} tenants={tenants} onSwitchTenant={onSwitchTenant} onLogout={onLogout} onCommand={() => setCmdOpen(true)} onOpenUsage={() => setView("usage")} />
       <ApprovalBar run={run} />
       <div className="relative flex min-h-0 flex-1">
         <LeftNav active={view} onSelect={setView} />

sundynix-desktop/frontend/src/lib/api.ts

@@ -139,6 +139,32 @@ export async function tenantCurrent(): Promise<TenantCtx | null> {
   };
 }
 
+// ---- 我所属的租户 + 切换活跃租户（多租户）----
+export interface MyTenant {
+  id: string;
+  name: string;
+  slug: string;
+  plan: string;
+  credit_balance_micro: number;
+  shared_billing: boolean;
+  members: number;
+}
+
+export async function myTenants(): Promise<{ tenants: MyTenant[]; active: string }> {
+  const res = guard401(await fetch(`${GATEWAY}/api/v1/me/tenants`, { headers: bearer() }));
+  if (!res.ok) return { tenants: [], active: "" };
+  const d = (await res.json()) as { tenants?: MyTenant[]; active?: string };
+  return { tenants: d.tenants ?? [], active: d.active ?? "" };
+}
+
+export async function switchTenant(tenantId: string): Promise<void> {
+  const res = guard401(await fetch(`${GATEWAY}/api/v1/me/tenant`, { method: "POST", headers: { "Content-Type": "application/json", ...bearer() }, body: JSON.stringify({ tenant_id: tenantId }) }));
+  if (!res.ok) {
+    const d = (await res.json().catch(() => ({}))) as { error?: string };
+    throw new Error(d.error ?? `switch failed: ${res.status}`);
+  }
+}
+
 // ---- 我的用量明细（当前用户自己租户：余额 + 按天趋势 + 最近消耗）----
 export interface UsageDay {
   day: string; // YYYYMMDD

sundynix-desktop/frontend/src/shell/TopBar.tsx

@@ -1,6 +1,6 @@
 import type { CSSProperties } from "react";
-import { User, ChevronDown, Search as SearchIcon, LogOut, Sun, Moon, Coins } from "lucide-react";
-import type { AuthUser, TenantCtx } from "../lib/api";
+import { User, ChevronDown, Search as SearchIcon, LogOut, Sun, Moon, Coins, Building2 } from "lucide-react";
+import type { AuthUser, TenantCtx, MyTenant } from "../lib/api";
 import { useHealth } from "../lib/health";
 import { isMacDesktop } from "../lib/desktop";
 import { useTheme } from "../lib/theme";
@@ -42,8 +42,31 @@ function CreditChip({ tenant, onClick }: { tenant: TenantCtx; onClick?: () => vo
   );
 }
 
+// 租户切换器：仅当用户属多个租户时显示；切换即改活跃租户（工作区 + 计费上下文）。
+function TenantSwitcher({ tenants, activeId, onSwitch }: { tenants: MyTenant[]; activeId?: string; onSwitch?: (id: string) => void }) {
+  if (tenants.length < 2) return null;
+  return (
+    <div className="relative" style={NODRAG}>
+      <Building2 className="pointer-events-none absolute left-2 top-1/2 h-3.5 w-3.5 -translate-y-1/2 text-slate-500" />
+      <select
+        value={activeId ?? ""}
+        onChange={(e) => onSwitch?.(e.target.value)}
+        title="切换当前租户（工作区 + 计费）"
+        className="appearance-none rounded-md border border-line bg-ink-800 py-1 pl-7 pr-7 text-xs text-slate-300 focus:border-brand focus:outline-none"
+      >
+        {tenants.map((t) => (
+          <option key={t.id} value={t.id}>
+            {t.name}
+          </option>
+        ))}
+      </select>
+      <ChevronDown className="pointer-events-none absolute right-2 top-1/2 h-3.5 w-3.5 -translate-y-1/2 text-slate-500" />
+    </div>
+  );
+}
+
 // 顶栏：品牌 · 垂直切换 · 健康灯 · 积分余额 · 登录用户 + 登出（深色 + 毛玻璃）。
-export function TopBar({ user, tenant, onLogout, onCommand, onOpenUsage }: { user: AuthUser; tenant?: TenantCtx | null; onLogout: () => void; onCommand?: () => void; onOpenUsage?: () => void }) {
+export function TopBar({ user, tenant, tenants = [], onSwitchTenant, onLogout, onCommand, onOpenUsage }: { user: AuthUser; tenant?: TenantCtx | null; tenants?: MyTenant[]; onSwitchTenant?: (id: string) => void; onLogout: () => void; onCommand?: () => void; onOpenUsage?: () => void }) {
   const h = useHealth();
   const { theme, toggle } = useTheme();
   return (
@@ -86,6 +109,7 @@ export function TopBar({ user, tenant, onLogout, onCommand, onOpenUsage }: { use
         <Light on={h.neo4j} label="Neo4j" />
       </div>
       <div className="ml-auto flex items-center gap-2" style={NODRAG}>
+        <TenantSwitcher tenants={tenants} activeId={tenant?.tenant?.id} onSwitch={onSwitchTenant} />
         {tenant?.tenant && <CreditChip tenant={tenant} onClick={onOpenUsage} />}
         <button
           onClick={toggle}