Copilot review: seeding with `value ?? defaultValue` also substitutes the
default when the raw value is an explicit `null` — a nullable number field the
user cleared, or one the server sent — where `resolveValue` previously kept the
null and the box rendered empty. A nullable schema with a non-null default
would have opened showing that default over a real value.
Test the `undefined` case explicitly, as `SchemaJsonField` already does, and
pin it: the new test fails with `'30'` where `''` belongs.
Signed-off-by: cliffhall <cliff@futurescale.com>
d3b70a6329