[ero-qt]

Closes #193.

The run_tasks example in the future module docs now only compiles its hidden use and async fn when alloc is on. Without alloc, the example is empty, so cargo test --no-default-features --features unity passes again.

cargo test --no-default-features --features unity --doc
test src\future\mod.rs - future (line 83) - compile ... ok
test result: ok. 21 passed; 0 failed; 15 ignored

With alloc, the whole example still compiles. I checked by putting a type error in it, which fails with alloc and is skipped without it.

[CryZe]

Reproduced the unresolved run_tasks import on master without alloc. With this change, the Unity doctests pass both without alloc (21 passed) and with alloc (23 passed), and all seven CI checks are green. No public API changes.

Non-blocking follow-up: CI should also run cargo test --no-default-features --features unity so allocation-free doctests are covered.