Code lens to run targets

Add code lenses above rule definitions that let users run `make ` directly from the editor. This is a common pattern in LSP servers for build systems and task runners, and would save users from having to switch to a terminal to invoke individual targets.

The issue names no files, tests, or entry points. Start by locating how rule definitions are parsed and how the LSP server handles code lenses; done means rule definitions show lenses that invoke `make ` directly from the editor.

Written by the indexing model from the issue text.