Include the requested version in the uninstall error output when the target is not installed.

Add a fast test to lock the behavior.

Close #3767

GitHub Copilot summary:

This pull request improves the error messaging in nvm.sh when attempting to uninstall a Node version that is not installed. It also adds a new test to verify the updated error message behavior.

Error handling improvements:

• Improved the error message in the nvm() function in nvm.sh to specify the requested version more clearly when an uninstall is attempted for a version that is not installed. Now, if the inferred version differs from the requested pattern, the message indicates which version was inferred; otherwise, it states the requested version is not installed.

Testing:

• Added a new test script test/fast/Running 'nvm uninstall' with an uninstalled version shows the requested version to ensure that uninstalling a non-installed version returns the correct error message.