🤖 refactor: use isWorkflowRunTaskId helper for drift check

#3565 reintroduced a hardcoded startsWith("wfr_") in WorkflowRunner's
nested-step drift detection. taskId.ts already exports the canonical
WORKFLOW_RUN_TASK_ID_PREFIX and isWorkflowRunTaskId() predicate as the
single source of truth for that prefix. Use the helper instead of the
duplicated literal; behavior is identical (both are falsy for a missing
taskId inside the find() predicate).

Author: mux-bot[bot]

src/node/services/workflows/WorkflowRunner.ts

@@ -15,6 +15,7 @@ import assert from "@/common/utils/assert";
 import { getErrorMessage } from "@/common/utils/errors";
 import { validateJsonSchemaSubset } from "@/common/utils/jsonSchemaSubset";
 import type { IJSRuntime, IJSRuntimeFactory } from "@/node/services/ptc/runtime";
+import { isWorkflowRunTaskId } from "@/node/services/tools/taskId";
 import { AsyncMutex } from "@/node/utils/concurrency/asyncMutex";
 import { AsyncSemaphore } from "@/node/utils/concurrency/asyncSemaphore";
 import type { ResolvedWorkflowAction, WorkflowActionRegistry } from "./WorkflowActionRegistry";
@@ -857,7 +858,7 @@ export class WorkflowRunner {
     const run = await this.runStore.getRun(runId);
     const driftedStep = run.steps.find(
       (step) =>
-        step.stepId === spec.id && step.inputHash !== inputHash && step.taskId?.startsWith("wfr_")
+        step.stepId === spec.id && step.inputHash !== inputHash && isWorkflowRunTaskId(step.taskId)
     );
     if (driftedStep != null) {
       throw new Error(