Full `docs/conf.py` rewrite targeting `pydata-sphinx-theme` 0.18
(3-col layout: nav-index left, content middle, page-toc right)
skinned to a minimal b&w look via `_static/css/custom.css`, keeping
the `algol_nu` pygments style.
Also add 2 local sphinx exts under `docs/_ext/`,
- `d2diagrams.py`: a `.. d2::` directive rendering `d2lang` sources
at build time when a `d2` bin is found (`D2_BIN` env supports
argful values eg. `'nix run nixpkgs#d2 --'`), falling back to any
git-committed SVG, else emitting the raw source as a literal
block; no pypi ext was usable (all stubs or returncode-swallowing
per the #157 research),
- `marginalia.py`: a theme-agnostic `.. margin::` directive
(`sphinx-book-theme` style `Sidebar` subclass) for prose-anchored
RHS asides; the custom css floats these (and `:margin:` d2 figs)
into the right gutter on wide screens.
(this patch was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code
Gud Boi