fix(config): align default.yaml with server schema

src/config/defaultYaml.test.ts

@@ -0,0 +1,23 @@
+import { describe, it, expect } from 'vitest';
+import { readFileSync } from 'fs';
+import { parse } from 'yaml';
+
+describe('config/default.yaml', () => {
+  it('does not use deprecated server.tailscale_only key', () => {
+    const raw = readFileSync('config/default.yaml', 'utf-8');
+    const parsed = parse(raw) as any;
+
+    expect(parsed).toBeTruthy();
+    expect(parsed.server).toBeTruthy();
+    expect(parsed.server.tailscale_only).toBeUndefined();
+  });
+
+  it('documents server.tailscale.* shape', () => {
+    const raw = readFileSync('config/default.yaml', 'utf-8');
+    const parsed = parse(raw) as any;
+
+    expect(parsed.server.tailscale).toBeTruthy();
+    expect(typeof parsed.server.tailscale).toBe('object');
+    expect(typeof parsed.server.tailscale.serve).toBe('boolean');
+  });
+});