Install scripts either globally or in a project

[freepicheep]

Added

• Added first-class script dependencies via [dependencies.scripts] with
  nuance add-script and nuance remove-script.
• Added script installation into .nu_scripts/ from a specific path in a git
  repo or gist clone URL.
• Added lockfile artifact kinds (module / script) and script path
  tracking for reproducible frozen installs.

Changed

• Switched module declarations from [dependencies] to
  [dependencies.modules].
• Updated activate.nu generation and nuance hook output to support both
  module and script dependency paths.
• Updated module install/activation to detect real module entry paths (including
  nupm-style nested layouts) by reading nupm.nuon metadata hints and scanning
  for mod.nu, then generating export use statements with the discovered
  path (for example nu-salesforce/nu-salesforce).