Move the plugin names, their env vars, the managed versions directory,
and the packaged-build gate into fabro-static so fabro-cli, fabro-server,
and fabro-dev stop each spelling the bundle out on their own. Fold the
three identical graph-render wrappers into one function, return Cargo's
target directory from the plugin build instead of walking parents, honor
CARGO_BUILD_TARGET in every plugin-build entry point, and tidy the
installer's plugin validation and the smoke script.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>