Action implementations for the script_author tool — the boundary over
YmerNode.Scripts's write verbs.
Same shape as YmerNode.Mcp.Tools.Scripts.Actions, and for the same reason:
every extracted scalar is guarded on its head, and each guarded head is
followed by a wrong-typed twin that answers a message rather than letting the
context's own guard raise. Two strings, nothing else — there is no range and
no vocabulary here, so there is no Validate layer.
create's response carries the stored script the way update and accept
do, rather than only its name: a caller that has just written a script wants
to see what the node made of it — the derived name most of all, since it never
supplied one.