test(release-cleanup): 補齊 cleanup/config/main 與新驗證函式測試

新增 cleanupReleases、cleanupOrphanTags 的失敗路徑與分類測試、
loadConfig 環境變數驗證測試、main 整合測試,以及 requireUrl/
requireRepository 與 content-type 檢查測試。測試共 41 項全數通過。

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/test/main.test.js

@@ -0,0 +1,43 @@
+import { test, afterEach } from 'node:test'
+import assert from 'node:assert/strict'
+import { main } from '../index.js'
+
+const realFetch = globalThis.fetch
+const savedEnv = { ...process.env }
+
+afterEach(() => {
+  globalThis.fetch = realFetch
+  process.env = { ...savedEnv }
+})
+
+function setEnv(env) {
+  for (const key of ['GITEA_SERVER_URL', 'GITEA_REPOSITORY', 'KEEP_COUNT', 'GITEA_TOKEN']) {
+    delete process.env[key]
+  }
+  Object.assign(process.env, env)
+}
+
+test('main 在環境變數有效且 API 正常時順利完成', async () => {
+  setEnv({
+    GITEA_SERVER_URL: 'https://gitea.example.com',
+    GITEA_REPOSITORY: 'owner/repo',
+    KEEP_COUNT: '2',
+  })
+  // 所有清單端點皆回空陣列(無 release、無 tag)
+  globalThis.fetch = async () => ({
+    ok: true,
+    status: 200,
+    headers: { get: () => 'application/json' },
+    json: async () => [],
+  })
+
+  await main() // 不應拋出
+})
+
+test('main 在必填環境變數缺失時 reject(供整合層級驗證錯誤處理)', async () => {
+  setEnv({
+    GITEA_REPOSITORY: 'owner/repo',
+    KEEP_COUNT: '2',
+  })
+  await assert.rejects(() => main(), /GITEA_SERVER_URL is required/)
+})