[Paururo]

What changes

• The How it works preview follows the reader's theme. assets/how-it-works.gif is now the light version and assets/how-it-works_dark.gif the dark one, following the repository's name / name_dark convention (as recore_logo and the benchmark figure do). Both were captured from the page at the same size, and each frame now has its own 256-colour palette, so the soft halo behind the drawings no longer shows bands (336 KB and 304 KB).
• The logo follows the theme again. docs: a README in the website's words that sends readers to the site #25 wrapped the logo's <picture> in a link to the website. GitHub's renderer then moves the <img> out of the <picture>, so the logo stayed light in dark mode and clicking it opened the SVG file. Both pictures are bare again; the website button under the logo and the caption under the preview still take readers to the site.

Checks

tools/check_site.py now fails if a <picture> sits inside a link in the README. It was broken on purpose (the logo wrapped in a link again) and caught it.

I checked the result with GitHub's own markdown API: both pictures come out as themed-picture with their image inside, and the light theme picks recore_logo.svg and how-it-works.gif while the dark theme picks the _dark files. Locally fmt, clippy, the tests, the build, check_site.py --run-tutorial and the auto-merge gate check all pass.