`x clippy` on library/ crates is finicky

This is a bit terse atm but I've been using clippy to lint the standard library a fair bit and wanted to make sure there's a record of the issues I've encountered. I'll try to update this as I learn more or issues are fixed.

• If you do x clippy std then it will block on any failing clippy lints on core (or other dependencies of std)
• --fix sometimes works but other times will complain about missing std. I'm not sure what causes this as it only happens sometimes. Running clippy without --fix appears to make --fix work again (or maybe it's a coincidence).
• There isn't a way to cross-check other platforms (conversely x check is able to cross-check but doesn't check tests)
• I don't think there's a good way to check only CI lints for specific crates? There's x clippy CI but that checks everything. There is also --ci true but that implies a lot of other things which may not be appropriate for local dev.

Start by reproducing the listed x clippy std, --fix, cross-platform, and CI-lint scenarios, comparing them with x check. Then inspect the x clippy and x check entry points to separate confirmed bugs from the reported coincidence; done means the selected behavior is reproducible and its intended workflow is validated.