cut: declare required positionals through cli arguments

[CMGS]

What

Seventeen commands checked their positional argument by hand and returned their own "must be given" error. They now declare it: utils.Positional(name, usage, max) builds a required cli.StringArgs (urfave/cli v3.11 carries Min/Max on the plural type only; max −1 is an id list), 27 commands use it, the actions read cmd.StringArgs(name) and the argIDs helper is gone.

Kept as they were: image build (its rule is exactly one argument, and a declared argument ignores extras) and workload dissociate (ids are optional when --node is given).

Behaviour change

A missing argument now fails before the action with urfave's message, printed through the logger with exit code 1, where it used to be a bare line with exit code 255:

$ eru-cli pod nodes
FTL run eru-cli error="sufficient count of arg pod not provided, given 0 expected 1" func=main.main
$ eru-cli pod nodes --help
USAGE:
   eru-cli pod nodes [options] pod name

Lines

Production −128 net (+63 −191), tests +8 net; comment delta +1 −0 (the helper's godoc carries the −1 convention).

Evidence

Gate on the branch: build, vet, full tests, make lint, make fmt-check and asl on both GOOS green; the two tests that pinned the old errors now assert the run fails before the action.