Respect self-constraints on recursive extras

[charliermarsh]

Summary

Sort of ridiculous, but today this passes, when it should fail:

[project]
name = "foo"
version = "0.1.0"
description = "Add your description here"
readme = "README.md"
requires-python = ">=3.13.0"
dependencies = []

[project.optional-dependencies]
async = [
    "foo[async]==0.2.0",
]