refactor(ui): remove never-typed ghost props from useDefinition ownProps

Replace the ChildrenProps intersection approach with ResolveBgProps,
which transforms the base type so that only the relevant children
variant exists in the final type. Provider components get
childrenWithBgProvider (with children Omit'd), non-providers pass
through unchanged — no more optional never properties showing up
in autocomplete.

Signed-off-by: Johan Persson <johanopersson@gmail.com>

.changeset/grumpy-towns-stick.md

@@ -0,0 +1,5 @@
+---
+'@backstage/ui': patch
+---
+
+Cleaned up `useDefinition` `ownProps` types to remove never-typed ghost properties from autocomplete.

packages/ui/src/hooks/useDefinition/types.ts

@@ -81,10 +81,19 @@ type ResolvedOwnProps<
   [K in keyof PropDefs & keyof P]: ResolvePropType<P[K], PropDefs[K]>;
 };
 
-type ChildrenProps<Bg extends 'provider' | 'consumer' | undefined> =
-  Bg extends 'provider'
-    ? { childrenWithBgProvider: ReactNode; children?: never }
-    : { children: ReactNode; childrenWithBgProvider?: never };
+type BaseOwnProps<
+  D extends ComponentConfig<any, any>,
+  P extends Record<string, any>,
+> = {
+  classes: Record<keyof D['classNames'], string>;
+} & ResolvedOwnProps<P, D['propDefs']>;
+
+type ResolveBgProps<
+  D extends ComponentConfig<any, any>,
+  TBase,
+> = D['bg'] extends 'provider'
+  ? Omit<TBase, 'children'> & { childrenWithBgProvider: ReactNode }
+  : TBase;
 
 type DataAttributeKeys<PropDefs> = {
   [K in keyof PropDefs]: PropDefs[K] extends { dataAttribute: true }
@@ -122,10 +131,7 @@ export interface UseDefinitionResult<
   D extends ComponentConfig<any, any>,
   P extends Record<string, any>,
 > {
-  ownProps: {
-    classes: Record<keyof D['classNames'], string>;
-  } & ResolvedOwnProps<P, D['propDefs']> &
-    ChildrenProps<D['bg']>;
+  ownProps: ResolveBgProps<D, BaseOwnProps<D, P>>;
 
   // Rest props excludes both propDefs keys AND utility prop keys
   restProps: keyof Omit<P, keyof D['propDefs'] | UtilityKeys<D>> extends never