applySchemaConstants only corrected top-level pinned fields, but the deep
link's overlay replaces a nested object wholesale rather than merging into it —
so `{ config: { kind: "sms" } }` slipped past a nested read-only
`kind: { const: "email" }` the form was displaying. It now recurses into
object-valued properties, resolving each one's own root union the same way.
Signed-off-by: cliffhall <cliff@futurescale.com>
a69cb58451