Add help page information to the less pager prompt again #16913
Description
Summary
When using less to view help pages, uv should use the LESS variable to set the prompt (-P) in a fail-safe way (either works or is silently ignored) to tell the user they're viewing uv help output and the command for which they're viewing it.
The LESS variable follows an odd format and may already have things in it (user specific customization). The prompt value may need to be cleaned/escaped for this.
Background: Previously uv would try to set the less prompt to: "uv help: ". However, busybox less would break when passed -P, breaking the paging functionality (#16015). It was also spotted that everything after and including the colon was being dropped which meant that this feature wasn't serving its intended purpose. #16908 removed -P to avoid triggering the busybox issue.
Example
Running uv help run and scrolling down, a user would continue to see information about the current page in the prompt (bottom left corner):
