refactor(agent): runAgent uses Agent upstreams only; deprecate legacy settings.pi fields

pi.provider / baseUrl / model / thinkingLevel / apiKeySecretRef are now
DEPRECATED_SETTINGS_FIELDS: kept in the schema for stored JSON, dropped
from PATCH /settings and from the settings sections, never read by the
server. runAgent fails with a clear message when no upstream is set.
The agent demo gate checks the default upstream provider; e2e seeds a
fake upstream as default. OpenAPI summaries say Agent upstream.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

apps/server/test/pi/upstreams.test.ts

@@ -13,7 +13,7 @@ import { ensureSetupToken } from "../../src/modules/auth-settings/auth-service.t
 import { createSecretStore, createSettingsReader } from "../../src/modules/auth-settings/provided.ts";
 import { createPiModule } from "../../src/modules/pi/index.ts";
 import { refreshPiTokens } from "../../src/modules/pi/refresh.ts";
-import { dbCredentialStore } from "../../src/modules/pi/store.ts";
+import { dbCredentialStore, setDefaultUpstream } from "../../src/modules/pi/store.ts";
 import type { ServerContext } from "../../src/modules/types.ts";
 import {
   Browser,
@@ -383,5 +383,13 @@ describe.skipIf(!hasPg)("Pi 上游(真实 PG)", () => {
     const d3 = await drive(env, h.ctx.capabilities, r3, new AbortController().signal);
     expect(d3).toMatchObject({ status: "failed" });
     expect(d3.message).toMatch(/已停用/);
+
+    // 没有默认上游:旧 settings.pi 字段不再兜底,直接失败
+    await setDefaultUpstream(h.ctx, null);
+    const r4 = await newRun(null);
+    const d4 = await drive(env, h.ctx.capabilities, r4, new AbortController().signal);
+    expect(d4).toMatchObject({ status: "failed" });
+    expect(d4.message).toMatch(/未配置 Agent 上游/);
+    await setDefaultUpstream(h.ctx, fake.id);
   });
 });