Record a WeasyPrint smoke run on Linux

[p13i]

Gap

The retained PDF evidence exercised Chrome on macOS. The
formal example explicitly states that WeasyPrint and Linux
were not tested.

Acceptance criteria

• Run the committed formal fixture through WeasyPrint on
  Linux.
• Record the WeasyPrint version, operating system, page
  count, and output hash.
• Rasterize and inspect every generated page.
• Keep the Chrome evidence separate so one backend run does
  not imply coverage for another.

Verification

Add the exact smoke command and its evidence check to the
pull request.

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Written by Codex