test: document awc Tokio runtime requirement

[robjtede]

Summary

• add an integration test that uses awc from a plain #[tokio::test]
• document the expected spawn_local panic when no LocalSet is present

[github-code-quality]

Code Coverage Overview

Languages: Rust

Rust / code-coverage/cargo-llvm-cov

The overall line coverage in commit 870b5ff in the awc-tokio-runtime-te... branch remains at 84%, unchanged from commit 51ccf75 in the main branch.

Show a line coverage summary of the most impacted files.

File	main 51ccf75	awc-tokio-runtime-te... 870b5ff	+/-
actix-http/src/h2/mod.rs	92%	89%	-3%
actix-http/src/h2/service.rs	63%	61%	-2%
actix-web-codegen/src/route.rs	75%	75%	0%
awc/src/middleware/redirect.rs	94%	94%	0%

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_{Updated August 24, 2026 22:52 UTC}