chore(changeset): declare the plugin-form customFields change as minor

Since the previous commit, TabbedFormSchema, WizardFormSchema and
SplitFormSchema declare `customFields`, which widens the package's public
type surface. A widening takes a minor level, so the changeset's level moves
from patch to minor. The body is unchanged.

Co-authored-by: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BP8CMtACxTdLjqR6rhd33C

Author: claude

.changeset/10254-sections-customfields-drawer-modal.md

@@ -1,5 +1,5 @@
 ---
-'@object-ui/plugin-form': patch
+'@object-ui/plugin-form': minor
 ---
 
 fix(plugin-form): `customFields` members render inside explicit `sections` on the drawer, modal, tabbed, wizard and split arms