- The name-based narrowing is extracted as `narrowBySuppliedNames` and used
by the CLI coercion as well as the form: an undiscriminated union whose
branches type a shared name differently was losing the coercion for every
argument, including the ones that identify the branch unambiguously. The
type-agreement fallback now also polls only the const-compatible branches.
- TUI missingRequiredFields accepts `null` only where the property admits it,
matching the web gate: branch fields are rendered optional, so a
`default: null` on a non-nullable required field reached the check and the
call went out with a value the schema rejects.
Signed-off-by: cliffhall <cliff@futurescale.com>