[LouisFaure]

Summary

This PR prepares the 0.2.0 release: it dates the release notes and fixes some dark-mode colours in the docs.

• Release notes: the 0.2.0 heading is dated 2026-11-12 instead of the-future. This is step 1 of Releasing in the contributing guide.
• Dark mode, lighter surfaces:
  • Code blocks, inline code and the boxes in the SVG diagrams go from oklch 25% to 31%. That matches the brightness of the surface on the stable docs, #29313d.
  • Cards, admonitions, tabs and notebook outputs go from 23% to 27%.
  • The page background stays the same, as bright as stable's #121212.
• Dark mode, tables: the first row no longer has the same shade as the header. Rows step down from the header at 22% and 25%, and the inner borders are sepia instead of slate.
• Dark mode, muted text: muted text goes from 67% to 71%. It is now at least 5:1 on every surface, including chart legends and diagram captions.
• Home page buttons: Pipeline overview and View Tutorials now use the logo green (secondary) instead of the theme's teal (success). On light, a darker shade of the same hue, #4d7c0f, keeps the text at 5.0:1 on white.

Light mode changes only for the two green buttons.

Testing

• A clean Sphinx build (sphinx-build -E -W --keep-going) succeeds.
• The pre-commit hooks pass on the changed files.
• Checked in the browser, in dark and light mode, on the home page, the Overview page (pipeline diagram, run-time charts and table) and the I/O page (Parquet layout and size diagrams). Contrast ratios were measured from the computed colours.

After merging

1. Run the GPU tests on the merge commit and check that Checks passes.
2. Tag the merge commit v0.2.0 and push the tag.
3. Create the GitHub release, which publishes to PyPI.
4. On main, start 0.2.1.md from blank.md.

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