fix(playwright): recognize modern screenshot comparison errors

[dimazollo]

Playwright 1.59.1 reports screenshot mismatches as:

Error: expect(page).toHaveScreenshot(expected) failed

The adapter only recognizes Screenshot comparison failed, so it marks these as general errors even when expected/actual/diff images are attached. Accept can then leave a stale error instead of resolving the visual failure.

This recognizes the newer page/locator and Buffer matcher headers, checking for matching diff attachments. Capture failures and unrelated assertion errors remain general errors; the old format still works. Only the adapter and its unit tests change. Platform handling is separate.

Reproduction

With Playwright 1.59.1 and html-reporter/playwright:

import {test, expect} from '@playwright/test';

test('screenshot mismatch', async ({page}) => {
    const color = process.env.CHANGED ? 'blue' : 'red';
    await page.setContent(`<div style="width:120px;height:80px;background:${color}"></div>`);
    await expect(page).toHaveScreenshot('example.png');
});

npx playwright test --update-snapshots
CHANGED=1 npx playwright test

Before: error / Error. After: fail / ImageDiffError.

Tests

• Seven regression cases fail before the fix; all 33 adapter tests pass after it.
• npm test passes on Node 20.19.6, based on upstream 11.16.2 (a4e797c).
• Checked actual Playwright 1.59.1 results: page, locator and Buffer diffs are recognized; mixed assertion failures and a capture timeout remain errors.

The full GUI e2e suite and interactive Accept/Undo weren't rerun for this isolated fix.

Draft in the personal fork; upstream submission is pending CLA confirmation.

[dimazollo]

Submitted upstream as gemini-testing#808. Closing this preparation draft without merging; the source branch is still in use by the upstream PR.