fix: add missing MigrateUserDataOnMerge to test stubs

Interface method added in agent-transfer branch was missing from
seedStubStore and createCaptureStore, breaking CI on main.

internal/bootstrap/seed_store_test.go

@@ -108,6 +108,9 @@ func (s *seedStubStore) EnsureUserProfile(_ context.Context, _ uuid.UUID, _ stri
 func (s *seedStubStore) PropagateContextFile(_ context.Context, _ uuid.UUID, _ string) (int, error) {
 	return 0, nil
 }
+func (s *seedStubStore) MigrateUserDataOnMerge(_ context.Context, _ []string, _ string) error {
+	return nil
+}
 
 // ---- Tests ----
 

internal/gateway/methods/agents_create_owner_test.go

@@ -101,6 +101,9 @@ func (s *createCaptureStore) EnsureUserProfile(_ context.Context, _ uuid.UUID, _
 func (s *createCaptureStore) PropagateContextFile(_ context.Context, _ uuid.UUID, _ string) (int, error) {
 	return 0, nil
 }
+func (s *createCaptureStore) MigrateUserDataOnMerge(_ context.Context, _ []string, _ string) error {
+	return nil
+}
 
 // ---- helpers ----