docs: Run mdbook tests on Hydroflow+ docs

[shadaj]

Not sure how feasible this actually is given that Stageleft is involved, but we need some solution to ensure that the docs aren't out of date. Maybe we should pull the snippets directly from Rust files or something.

[MingweiSamuel]

Maybe we should pull the snippets directly from Rust files or something.

Yeah I set up some stuff for this for the hydroflow quickstart examples

hydroflow/docs/docs/hydroflow/quickstart/example_5_reachability.mdx

Lines 55 to 67 in 4bdd556

	<CodeBlock language="rust" showLineNumbers>{exampleCode}</CodeBlock>
	And now we get the full set of vertices reachable from `0`:
	<CodeBlock language="console">{extractOutput(exampleOutput)}</CodeBlock>
	## Examining the Hydroflow Code
	Let's review the significant changes here. First, in setting up the inputs we have the
	addition of the `reached_vertices` variable, which uses the [union()](../syntax/surface_ops_gen.md#union)
	op to union the output of two operators into one.
	We route the `origin` vertex into it as one input right away:
	<CodeBlock language="rust">{getLines(exampleCode, 8, 12)}</CodeBlock>

[MingweiSamuel]

(half completed in #1318)

[shadaj]

Infra set up in #1592, we inline documentation as doctests to ensure they compile.