POST /api/cases takes an optional path; Add Case > Create New gets a 'Create in a
custom folder' option with Browse. The folder is created (or an empty one filled),
scaffolded like a normal case and registered as a linked case. System, home,
credential and Codeman folders are refused; a folder with files is Link Existing's
job; a failure after the first write undoes what this call created. Admin only in
multi-user mode, like Link Existing.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
