examples: migrate async sleep to futures-timer; drop async-std

[VitalyAnkh]

Objective

• Fixes example async_compute.rs uses the discontinued async-std #19055

Solution

• Replace async-std with futures-timer.

Testing

CI

[VitalyAnkh]

I’d prefer to list async-io as a direct dependency of this example rather than of Bevy itself. Although Bevy adds async-std as dev-dependency, it appears to be used only here. What do you think?

[alice-i-cecile]

I'm okay with that but I had no idea that was possible. Can you make the change to demonstrate?

[VitalyAnkh]

The plan is to package the async‑compute examples like the mobile example then we could specify dependencies in Cargo.toml (

bevy/examples/mobile/android_basic/Cargo.toml

Line 14 in 0b48587

[dependencies]

), but since dev-dependencies don’t affect runtime, the current arrangement works fine.

This should be ready for merging now.

[alice-i-cecile]

@VitalyAnkh CI is failing due to web build failures, can you please take a look?

[VitalyAnkh]

Sure, I'm looking into the CI failures.

[VitalyAnkh]

I'm confused, the CI passed without changes but merging main: https://github.com/bevyengine/bevy/actions/runs/17226805596/job/48873622621?pr=19113#logs. @alice-i-cecile Alice, could you take a look?

[james7132]

Looks like it was a transient failure.

[VitalyAnkh]

run-examples-on-wasm still fails. I need to solve the problem.

[VitalyAnkh]

errno, which async-io depends, doesn't support target wasm32-unknown-unknown: lambda-fairy/rust-errno@a9bd71e.

[VitalyAnkh]

Since async-io doesn't support Timer on wasm target and we only need a Timer here, I'm going to use https://github.com/async-rs/futures-timer instead.

[VitalyAnkh]

This is ready to go now.