Presets

A preset bundles templates under a useful name, such as "RNA-seq", so people do not have to reconstruct the same selection for each folder. Presets are read from presets/, one file per preset; the filename is the preset key. Add this to presets/example.nix:

{
  displayName = "Example analysis";
  description = "A small starting point.";
  sortKey = 0;
  templates = [ "hello" ];
}

templates is required and every entry must be a loaded template; description and sortKey default to null, and displayName must be a string. An unknown template fails evaluation with Preset `<name>` references unknown templates: <list>..

A folder must choose exactly one of preset = "example"; or templates = [ "hello" ];. The selection does not remove the folder's steps or filter its contents; it decides which templates appear directly in the folder's New menu, and the remaining templates stay available under Other types. When someone creates a folder, it starts with the same template selection as the folder where the action was used: the same preset, or the same custom template list.