Rename and/or move a folder

Sets the folder's name AND parentId in one write. Both fields are a true replace, and that is the trap: parentId is applied exactly as sent, so OMITTING it (or sending null) MOVES THE FOLDER TO THE ROOT. To rename without moving, re-send the folder's current parentId.

name is required and trimmed; blank is a 400.

Cycles are refused: a folder cannot be its own parent and cannot be moved into one of its own descendants. A parentId outside this workspace reads as "parent folder not found".

The response is only an acknowledgement {id, updated: true} — it does NOT return the updated folder. Re-list if you need the new state.