fix(test): fix fs mock default wrapper in erp-error-context test

The vi.mock('fs') factory returned { default: { ... } } causing fs.mkdirSync
to be undefined at runtime. Add top-level exports alongside default for ESM/CJS interop.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/unit/services/erp/erp-error-context.test.ts

@@ -19,7 +19,12 @@ vi.mock('fs', () => ({
     existsSync: vi.fn(() => true),
     readdirSync: vi.fn(() => []),
     statSync: vi.fn()
-  }
+  },
+  mkdirSync: vi.fn(),
+  writeFileSync: vi.fn(),
+  existsSync: vi.fn(() => true),
+  readdirSync: vi.fn(() => []),
+  statSync: vi.fn()
 }))
 
 import { capturePageContext } from '../../../../src/main/services/erp/erp-error-context'