test: add tests for Windows polyfill, platform constants, and Node server resolution

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

browse/test/platform.test.ts

@@ -0,0 +1,37 @@
+import { describe, test, expect } from 'bun:test';
+import { TEMP_DIR, isPathWithin, IS_WINDOWS } from '../src/platform';
+
+describe('platform constants', () => {
+  test('TEMP_DIR is /tmp on non-Windows', () => {
+    if (!IS_WINDOWS) {
+      expect(TEMP_DIR).toBe('/tmp');
+    }
+  });
+
+  test('IS_WINDOWS reflects process.platform', () => {
+    expect(IS_WINDOWS).toBe(process.platform === 'win32');
+  });
+});
+
+describe('isPathWithin', () => {
+  test('path inside directory returns true', () => {
+    expect(isPathWithin('/tmp/foo', '/tmp')).toBe(true);
+  });
+
+  test('path outside directory returns false', () => {
+    expect(isPathWithin('/etc/foo', '/tmp')).toBe(false);
+  });
+
+  test('exact match returns true', () => {
+    expect(isPathWithin('/tmp', '/tmp')).toBe(true);
+  });
+
+  test('partial prefix does not match (path traversal)', () => {
+    // /tmp-evil should NOT match /tmp
+    expect(isPathWithin('/tmp-evil/foo', '/tmp')).toBe(false);
+  });
+
+  test('nested path returns true', () => {
+    expect(isPathWithin('/tmp/a/b/c', '/tmp')).toBe(true);
+  });
+});