Python: bind `timed`

[0-jake-0]

StreamOps::timed (crates/wingfoil/src/fluent.rs, next to print) passes each value through unchanged and prints a performance summary at the end of the run. It is not exposed in Python — grep -rn '\btimed\b' crates/wingfoil-python/src finds only unrelated hits.

Its neighbour print is bound, and the two are the same shape, so this is a small, well-modelled first contribution to the Python crate.

Where to start

PyStream::print in crates/wingfoil-python/src/graph.rs (~line 662) is the model. The binding is one line over the erased PyElement edge plus rustdoc:

pub fn timed(&self) -> PyStream {
    self.wrap(self.stream.timed())
}

Check the bound before assuming it compiles: timed wants T: Clone + Default + 'static and PyElement satisfies that (print additionally needs Debug and gets it). If it does not compile, say so on the issue rather than working around it — that would be a real finding about the erased edge.

The recipe for the Python step is /new-op §7 (.claude/commands/new-op.md), which distinguishes the one-line forward (an op whose Out is T, which this is) from the hand-written register_op1 needed for tuple outputs.

Acceptance criteria

• PyStream::timed exists, with rustdoc saying what it prints and when (end of run, not per tick).
• A Rust-side unit test in graph.rs's mod tests, next to the print / inspect ones, asserting values pass through unchanged.
• A pytest under crates/wingfoil-python/tests/ covering the same from the Python side.
• If the readthedocs API page lists methods explicitly (crates/wingfoil-python/docs/), timed is added there too.
• cd crates/wingfoil-python && maturin develop && pytest passes; cargo fmt --all and cargo lint-all clean.

Branch from main, target base main. See CONTRIBUTING.md.

[maxi-maxima]

I can take this. I'll mirror PyStream::print with a one-line erased-edge imed() forward, add the Rust-side binding regression and Python pass-through test from the acceptance criteria, and update any explicit Python API method list. I'll verify the focused Rust/Python paths plus fmt and lint before opening the PR.