feat: add Step/StepMut/StepWith/StepWithMut traits

[schell]

Formalizes the pull-based step event-loop convention (used across mogwai, iti, mogwai-beads, house-ui, privateer, etc.) as four traits in a new step.rs module.

• Step: &self — for event-listener-only widgets (enables concurrent racing)
• StepMut: &mut self — for widgets that mutate their own fields
• StepWith<T>: container racing per-child futures via closure (&self)
• StepWithMut<T>: container racing per-child futures via closure (&mut self)

RPITIT returns (not object-safe), Output: 'static. Non-breaking — existing inherent step methods are unaffected.

Closes beads schell-09d.

[Copilot]

Pull request overview

Adds a new step module to formalize Mogwai’s pull-based “step” event-loop convention as reusable traits, enabling more generic composition patterns (e.g., containers racing child futures) across the ecosystem.

Changes:

• Introduces Step, StepMut, StepWith<T>, and StepWithMut<T> traits in a new crates/mogwai/src/step.rs module.
• Exposes the new module from lib.rs and re-exports the traits via prelude::* and (when enabled) future.
• Bumps mogwai crate version and updates the mogwai-macros dependency version.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
crates/mogwai/src/step.rs	Adds the four stepping traits and module-level documentation/examples.
crates/mogwai/src/lib.rs	Exposes the new step module and re-exports it via the prelude.
crates/mogwai/src/future.rs	Re-exports step traits and updates module docs to mention composition with race_all.
crates/mogwai/Cargo.toml	Version bump and mogwai-macros dependency version update.

Suppressed comments (1)

crates/mogwai/src/step.rs:190

• The step_with_mut callback type uses dyn Future + '_ without tying that lifetime to the &mut T argument. This can prevent returning futures that legitimately borrow from the provided child reference. Use an explicit higher-ranked bound so the returned boxed future is allowed to live for exactly as long as each child borrow.

    fn step_with_mut<Ev>(
        &mut self,
        f: impl FnMut(&mut T) -> Pin<Box<dyn Future<Output = Ev> + '_>>,
    ) -> impl Future<Output = Self::Output>
    where

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[schell]

Keeping the prelude re-export by design — the step convention is intended to be the idiomatic way all mogwai widgets advance, so the traits belong in the prelude alongside view::* and proxy::*. The name-conflict risk is accepted: Step/StepMut/StepWith/StepWithMut are novel names unlikely to collide with user types, and any downstream that has its own Step trait can disambiguate with explicit imports.