Helper CTA about install vs pin is confusing when not in a project

[charlespierce]

In #1417, we added additional text to the success message after running volta install that has a call-to-action for using volta pin to change a local project's pinned version.

However, this text is always shown, regardless of whether the command is run from a project or not. It's a bit confusing to see that CTA when you run volta install node initially to set up a default version and aren't in a project.

Based on the underlying issue (#1311), I believe the core issue is actually that the info_project_version text isn't clear what the user can do to resolve the problem. I suspect we should move that additional text over to info_project_version, so that it's shown only when in a project that has a pinned version.

Additionally, right now it's using the full Node + npm version, so recommends an invalid command, e.g.:

to use node@20.16.0 (with npm@10.8.1) in this project run `volta pin node@20.16.0 (with npm@10.8.1)`