The App deep link seeded defaults and spread its `appArgs` over them, which
replaces a nested object wholesale: `{ config: { kind: "sms" } }` discarded
the nested SMS branch's own defaults, which the form then displayed while the
submitted arguments omitted them. New seedSchemaValues merges the two per
level, picking each nested branch from the nested values, and the supplied
value still wins wherever the two meet.
Signed-off-by: cliffhall <cliff@futurescale.com>