refactor(typing): add annotations to `ext.commands.help`

[shiftinv]

Summary

see title - pretty straightforward.

The end goal is getting --verifytypes to pass on the entire project, but that still needs some further work.

Also included are a couple tiny documentation changes to match the runtime types, but nothing special.

Checklist

• [x] If code changes were made, then they have been tested
  • [x] I have updated the documentation to reflect the changes
  • [x] I have formatted the code properly by running task lint
  • [x] I have type-checked the code by running task pyright
• [ ] This PR fixes an issue
• [ ] This PR adds something new (e.g. new method or parameters)
• [ ] This PR is a breaking change (e.g. methods or parameters removed/renamed)
• [ ] This PR is not a code change (e.g. documentation, README, ...)

[shiftinv]

~~Depends on #847.~~ merged.