collectSchemaDefaults recursed only when a nested object declared `properties`
directly, so one keeping its fields on a composition branch was skipped — while
SchemaForm rendered that branch and displayed its read-only discriminator. The
constant was shown and never submitted, and the server rejected the call. The
recursion now gates on declaresAnyFields.
Signed-off-by: cliffhall <cliff@futurescale.com>