fix(FN-000): harden workflow merge classification

Address PR #1579 feedback by classifying PR merge statuses explicitly and preventing diagnostic audit failures from re-running a completed merge primitive.

packages/engine/src/__tests__/workflow-merge-nodes.test.ts

@@ -31,10 +31,22 @@ describe("workflow merge nodes", () => {
       outcome: "failure",
       value: "file-scope-violation",
     });
+    expect(classifyMergePrimitiveResult({ status: "merged-requested" }, undefined, "failure")).toEqual({
+      outcome: "success",
+      value: "merged-requested",
+    });
+    expect(classifyMergePrimitiveResult({ status: "stale-head" }, undefined, "failure")).toEqual({
+      outcome: "failure",
+      value: "stale-head",
+    });
     expect(classifyMergePrimitiveResult(undefined, "transient-failure", "failure")).toEqual({
       outcome: "success",
       value: "transient-failure",
     });
+    expect(classifyMergePrimitiveResult(undefined, "merged-requested", "failure")).toEqual({
+      outcome: "success",
+      value: "merged-requested",
+    });
   });
 
   it("runs the existing merge primitive and emits a workflow capability audit event", async () => {
@@ -58,4 +70,21 @@ describe("workflow merge nodes", () => {
       contextPatch: { mergedBranch: "main", "workflow:merge-status": "merged" },
     });
   });
+
+  it("does not retry the merge primitive when audit fails after classification", async () => {
+    const audit = vi.fn().mockRejectedValue(new Error("audit unavailable"));
+    const requestMerge = vi.fn().mockResolvedValue({
+      outcome: "success",
+      data: { status: "merged" },
+    });
+
+    const result = await runWorkflowMergeAttemptNode({ primitives: { requestMerge, audit } }, ctx, task);
+
+    expect(requestMerge).toHaveBeenCalledTimes(1);
+    expect(result).toEqual({
+      outcome: "success",
+      value: "merged",
+      contextPatch: { "workflow:merge-status": "merged" },
+    });
+  });
 });

packages/engine/src/workflow-merge-nodes.ts

@@ -13,11 +13,15 @@ export async function runWorkflowMergeAttemptNode(
 ): Promise<WorkflowNodeResult> {
   const result = await deps.primitives.requestMerge(ctx, task);
   const classified = classifyMergePrimitiveResult(result.data, result.value, result.outcome);
-  await deps.primitives.audit(ctx, {
-    type: "workflow-merge-node",
-    message: `workflow merge node classified ${classified.value ?? classified.outcome}`,
-    metadata: { taskId: task.id, primitiveOutcome: result.outcome, primitiveValue: result.value, primitiveData: result.data },
-  });
+  try {
+    await deps.primitives.audit(ctx, {
+      type: "workflow-merge-node",
+      message: `workflow merge node classified ${classified.value ?? classified.outcome}`,
+      metadata: { taskId: task.id, primitiveOutcome: result.outcome, primitiveValue: result.value, primitiveData: result.data },
+    });
+  } catch {
+    // Audit is diagnostic; a transient audit failure must not re-run the merge primitive.
+  }
   return {
     outcome: classified.outcome,
     value: classified.value,
@@ -42,7 +46,13 @@ export function classifyMergePrimitiveResult(
   if (data?.status === "failed") {
     return classifyMergeFailure(data.reason);
   }
-  if (value === "transient-failure" || value === "manual-required" || value === "stale-head" || value === "not-actionable") {
+  if (data?.status === "merged-requested") {
+    return { outcome: "success", value: "merged-requested" };
+  }
+  if (data?.status === "stale-head") {
+    return { outcome: primitiveOutcome, value: "stale-head" };
+  }
+  if (value === "transient-failure" || value === "manual-required" || value === "stale-head" || value === "not-actionable" || value === "merged-requested") {
     return { outcome: "success", value };
   }
   return { outcome: primitiveOutcome, value };