feat(swarm): add server file system utility for archetypes

tests/server/beads-fs.test.ts

@@ -0,0 +1,9 @@
+import { expect, test, describe } from 'bun:test';
+import { getArchetypes } from '../../src/lib/server/beads-fs';
+
+describe('beads-fs', () => {
+    test('getArchetypes returns array of archetypes', async () => {
+        const archetypes = await getArchetypes();
+        expect(Array.isArray(archetypes)).toBe(true);
+    });
+});