This change:

- Moves the docs generation from `build` to `bin`
- Makes it a prereq for `docs` task

If you think this is a step in the right direction, I'd love to also
move the CLI docs to be generated (and so some more docs-gen)

I have a PoC/WIP of generating the rest of the `configuration.md` docs
from `Config.pkl` [here](#447) (also
planning on doing the `builtins`)

# Alternatives

I first tried to use a ["data
loader"](https://vitepress.dev/guide/data-loading#basic-usage) to load
the TOML and Vue templates to render the data. That worked until it was
time to render the doc string. You can't have it render Markdown, since
Vue is later in the pipeline than Markdown. Womp Womp.

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Generates `docs/gen/settings-config.md` from `settings.toml` using a
new Rust bin, includes it in `configuration.md`, and wires the generator
into docs tasks and CI.
> 
> - **Docs generation**:
> - Add new bin `generate-docs` (`bin/generate_docs.rs`) to produce
`docs/gen/settings-config.md` from `settings.toml` using shared types in
`build/settings_toml.rs`.
> - Replace large inline section in `docs/configuration.md` with
`<!--@include: ./gen/settings-config.md-->`.
>   - Update `docs/.gitignore` to ignore `gen/`.
> - Update `mise.toml` tasks: add `docs:gen` (runs `cargo run --bin
generate-docs`) and make `docs`/`docs:build` depend on it.
> - **Build script refactor**:
> - Extract settings TOML types to `build/settings_toml.rs`; update
`build/mod.rs` to expose it.
> - Simplify `build/generate_settings.rs` to import shared types and
remove in-build docs generation.
> - **CI (Docs workflow)**:
>   - Trigger on `settings.toml` changes; add `Swatinem/rust-cache`.
> - Build via `mise run docs:build`; adjust `.nojekyll` path to
`docs/.vitepress/dist/.nojekyll`.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
f53d2a2. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->