site-setup: stop navigating to goals from back/next paths

The design-setup and import-capture back buttons and the goBack/goNext
fallbacks still routed to the goals step. Repoint them to exit the flow so
no UI path navigates to goals ahead of the step's removal. The goals step
itself is unchanged here.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: taipeicoder

client/landing/stepper/declarative-flow/flows/site-setup-flow/site-setup-flow.ts

@@ -392,7 +392,7 @@ const siteSetupFlow: Flow = {
 
 			switch ( currentStep ) {
 				case 'design-setup':
-					return navigate( 'goals' );
+					return exitFlow( `/home/${ siteId ?? siteSlug }` );
 
 				case 'importList': {
 					if ( backToStep ) {
@@ -454,14 +454,14 @@ const siteSetupFlow: Flow = {
 					return navigate( `import?siteSlug=${ siteSlug }` );
 
 				case 'import':
-					return navigate( 'goals' );
+					return exitFlow( `/home/${ siteId ?? siteSlug }` );
 
 				case 'verifyEmail':
 				case 'trialAcknowledge':
 					return navigate( `importerWordpress?${ urlQueryParams.toString() }` );
 
 				default:
-					return navigate( 'goals' );
+					return exitFlow( `/home/${ siteId ?? siteSlug }` );
 			}
 		};
 
@@ -471,7 +471,7 @@ const siteSetupFlow: Flow = {
 					return navigate( 'importList' );
 
 				default:
-					return navigate( 'goals' );
+					return exitFlow( `/home/${ siteId ?? siteSlug }` );
 			}
 		};