Fix remaining CI failures in PDF exporter test coverage branch

[Copilot]

This PR clears the remaining PR CI failures: rector/lint were blocked by one outdated assertion pattern, and commitlint/dco were blocked by branch history metadata. The change keeps the test intent intact while aligning the branch with repository CI policy.

• Test assertion cleanup

  • Replaced the last strpos(...) !== false assertion in SinglePagePdfExporterTest with a direct PHPUnit string assertion.
  • This removes the Rector diff and keeps the expectation readable alongside the adjacent PDF content checks.

• Commit policy compliance

  • Reworked the branch commit history to use conventional commit messages.
  • Added Signed-off-by trailers so the branch satisfies DCO enforcement.

• Affected surface

  • /tests/Unit/Pdf/SinglePagePdfExporterTest.php
  • PR commit metadata only; no production code changes

self::assertStringContainsString(
    "1 0 obj\n<< /Type /Catalog /Pages 2 0 R >>\nendobj\n2 0 obj",
    $rendered,
);

Original prompt

Estamos na main, porém quando rodo o composer mutation:test, está retornando muitos problemas, quero que resolva todos. Crie uma branch para isto, siga DCO, um commit por arquivo com -s, em todos os commits eu devo ser o autor. Siga conventional commits. Quero que este teste fique com tudo verde.

The user has attached the following file paths as relevant context:

• .github/copilot-instructions.md

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