sciagent code + Gitea Actions CI/CD

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

shared/vitest.config.ts

@@ -0,0 +1,10 @@
+import { defineConfig } from 'vitest/config';
+
+// Pure-logic unit tests for the shared kernel. `node` env is enough — the helpers
+// under test use only Web globals (fetch/Blob/File/Response) available in Node 20+.
+export default defineConfig({
+  test: {
+    environment: 'node',
+    include: ['src/**/*.test.ts'],
+  },
+});