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]>

apps/server/test/api-registry.test.ts

@@ -81,6 +81,9 @@ describe("Api 注册表鉴权标注", () => {
         "POST /pi/upstreams/{id}/oauth/start",
         "POST /pi/upstreams/{id}/oauth/complete",
         "POST /pi/upstreams/{id}/oauth/logout",
+        // PI-2 获取模型列表(会用上游凭证出站)
+        "POST /pi/upstreams/{id}/models/refresh",
+        "POST /pi/models/probe",
         // W7-C 定时任务看板:全部只接受控制台会话
         "GET /schedules",
         "POST /schedules",