Failure when `toMatchSnapshot('file')` has no filename extension specified in `'file'` string

**Describe the bug**

Failure when image snapshot has no filename extension

**To Reproduce**

See https://github.com/microsoft/playwright/issues/13414

**Expected behavior**

-------^

**Screenshots**

**Desktop (please complete the following information):**

**Smartphone (please complete the following information):**

**Additional context**

Start with the `toMatchSnapshot('file')` entry point and review the linked Playwright issue for the extensionless image-snapshot failure. Reproduce the case and trace the snapshot filename handling; done means an image snapshot path without a filename extension no longer fails.

Written by the indexing model from the issue text.