feat: explain refusals to delete or rerun an unfinished run

Gitea refuses to delete or rerun a run that has not finished with "this
workflow run is not done". Report "run 37 has not finished; cancel it first:
tea run cancel 37", and cover the next steps added to refusals in tests.

Signed-off-by: bircni <bircni@icloud.com>

internal/app/errors.go

@@ -186,6 +186,10 @@ func conflictHint(ctx context.Context, apiErr *transport.APIError, conflict *ser
 		if conflict.Key != "" {
 			return "enable it with: tea workflow enable " + conflict.Key
 		}
+	case services.ReasonNotDone:
+		if conflict.Kind == "run" && conflict.Key != "" {
+			return "cancel it first: tea run cancel " + conflict.Key
+		}
 	case services.ReasonOwnsRepos:
 		return "transfer or delete them first"
 	}