pub fn offer_vscode_extension()Expand description
Offer to install the editor extension, once ever, when a VS Code-family editor is present.
This asks rather than installs because the editor is not dev-prune’s territory the
way its own config directory is. Every gate below is a way of making sure a person
is actually there to answer: no marker yet, not a CI runner or container, both ends
of the terminal attached. When no editor is found nothing is written, so installing
one later and re-running devp setup still gets the one offer.