refactor: add typed query failure signals

sdk/src/query-failure-classification.ts

@@ -1,3 +1,11 @@
+import { GSDToolsError } from './gsd-tools-error.js';
+
+export interface QueryFailureSignal {
+  kind: 'timeout' | 'failure';
+  message: string;
+  timeoutMs?: number;
+}
+
 export function errorMessage(error: unknown): string {
   return error instanceof Error ? error.message : String(error);
 }
@@ -22,3 +30,19 @@ export function isTimeoutLikeError(error: unknown): boolean {
 export function timeoutMessage(command: string, args: string[], timeoutMs: number): string {
   return `gsd-tools timed out after ${timeoutMs}ms: ${command} ${args.join(' ')}`;
 }
+
+export function toFailureSignal(error: unknown): QueryFailureSignal {
+  if (error instanceof GSDToolsError && error.classification) {
+    return {
+      kind: error.classification.kind,
+      message: error.message,
+      timeoutMs: error.classification.timeoutMs,
+    };
+  }
+
+  const message = errorMessage(error);
+  if (isTimeoutMessage(message)) {
+    return { kind: 'timeout', message, timeoutMs: parseTimeoutMs(message) };
+  }
+  return { kind: 'failure', message };
+}