feat(pi): fetch and refresh upstream model lists, searchable model picker

- POST /pi/upstreams/{id}/models/refresh calls the provider's model list
  endpoint (OpenAI-shaped /models, Anthropic /v1/models, Google
  /v1beta/models, OpenRouter /api/v1/models; Radius via pi-ai refresh),
  normalizes {id, displayName, contextWindow, supportsVision,
  supportsTools, pricing} and stores it in pi_upstream.models (0044)
- GET .../models returns {source, fetchedAt, models[]}: remote merged
  with the static catalog (remote first); failures (401/network/
  unsupported) fall back to static with a one-line error
- POST /pi/models/probe for trying credentials before creating
- wizard and edit drawer: fetch button, searchable dropdown with
  vision/tool tags, manual id, source line; default upstream needs a model
- tests: mock /models, 401, network failure; smoke step; runbook

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

packages/db/migrations/0044_upstream_models.ts

@@ -0,0 +1,23 @@
+import type { Kysely } from "kysely";
+import { execDdl } from "../src/migration-helpers.ts";
+
+// PI-2 上游模型列表:「获取模型列表」从上游的模型列表接口拉到的结果(归一化后的 [{id, displayName, contextWindow,
+// supportsVision, supportsTools, pricing}])存 models,拉取时间存 models_fetched_at。null = 从没拉过,用随包静态表。
+
+// biome-ignore lint/suspicious/noExplicitAny: 迁移不依赖应用表类型
+export async function up(db: Kysely<any>): Promise<void> {
+  await execDdl(
+    db,
+    `alter table pi_upstream add column models jsonb;
+alter table pi_upstream add column models_fetched_at timestamptz;`,
+  );
+}
+
+// biome-ignore lint/suspicious/noExplicitAny: 同上
+export async function down(db: Kysely<any>): Promise<void> {
+  await execDdl(
+    db,
+    `alter table pi_upstream drop column if exists models_fetched_at;
+alter table pi_upstream drop column if exists models;`,
+  );
+}