CLI: first-class enum input -> flag (single --mode=a|b for a one-axis choice)

[bdelanghe]

Problem

When a verb's behavior is a single mutually-exclusive choice (mode A vs mode B), the natural model is one enum flag, e.g. --scope changed|all. It is unclear/undocumented how a z.enum([...]) input surfaces as a CLI flag, so authors fall back to multiple booleans — which then run into the "no boolean negation" gap (separate issue) and end up as two+ flags for one axis.

Request

• First-class, documented mapping of a z.enum([...]) input to a CLI flag (--flag value, validated against the enum members, shown in help).
• And/or a mutually-exclusive flag-group construct so a set of booleans can be declared as "pick at most one".