docs(arrow-convert): add a compile-checked doctest for reading ArrowData back into Rust

[phil-opp]

🤖 Machine-generated PR. Opened by Claude (Anthropic) during an automated code-review pass of the repository. Please review carefully before merging.

Issue

ArrowData (libraries/arrow-convert/src/lib.rs) is the type every dora node receives its inputs as, and the TryFrom<&ArrowData> impls are the read counterpart to IntoArrow. But ArrowData carried only a single-line doc comment, and the conversions were exercised only by #[cfg(test)] unit tests — there was no compile-checked example documenting the intended read pattern or its null/type contract.

IntoArrow (the Rust→Arrow direction) already has a good runnable doctest; the inverse direction had none.

Fix

Expand the ArrowData doc comment with a runnable # Example that:

• round-trips a Vec<f32> through IntoArrow → ArrowData → try_into (both Vec<f32> and borrowed &[f32]);
• converts a single-element array to a scalar (u8);
• shows that a type mismatch is a recoverable Err, not a panic.

Pure documentation addition — no code behavior changes.

Validation

• cargo test -p dora-arrow-convert --doc — the new doctest (and the existing IntoArrow one) pass.
• cargo fmt --all -- --check — clean.

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Generated by Claude Code

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[phil-opp]

Automated review by Claude — fully automated, no human in the loop.

No issues found. The doctest exercises the real TryFrom<&ArrowData> impls for Vec<f32>, &[f32], and scalar u8 (generated via impl_try_from_arrow_data!), round-trips through IntoArrow -> ArrowData -> try_into, and correctly demonstrates the recoverable-error path: a Vec<i64> from a Float32Array resolves through as_primitive_opt::<Int64Type>() returning None -> Err, i.e. an eyre::Report, not a panic. arrow and eyre are non-dev dependencies, so the doctest builds under default features. Meaningful, non-trivially-passing assertions.

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Generated by Claude Code

[phil-opp]

Closing as a duplicate of #3084, which documents the same API more completely: it states the contract of both conversion shapes (scalar conversions require exactly one element and no nulls; slice/Vec conversions accept any length but reject nulls) rather than only demonstrating calls. The borrowed &[f32] example from this PR is worth grafting onto it.