fix(infra): treat undici fetch failed as transient unhandled rejection

src/infra/unhandled-rejections.test.ts

@@ -79,6 +79,12 @@ describe("isTransientNetworkError", () => {
     expect(isTransientNetworkError(error)).toBe(true);
   });
 
+  it("returns true for fetch failed with unclassified cause", () => {
+    const cause = Object.assign(new Error("unknown socket state"), { code: "UNKNOWN" });
+    const error = Object.assign(new TypeError("fetch failed"), { cause });
+    expect(isTransientNetworkError(error)).toBe(true);
+  });
+
   it("returns true for nested cause chain with network error", () => {
     const innerCause = Object.assign(new Error("connection reset"), { code: "ECONNRESET" });
     const outerCause = Object.assign(new Error("wrapper"), { cause: innerCause });

src/infra/unhandled-rejections.ts

@@ -94,12 +94,10 @@ export function isTransientNetworkError(err: unknown): boolean {
     return true;
   }
 
-  // "fetch failed" TypeError from undici (Node's native fetch)
+  // "fetch failed" TypeError from undici (Node's native fetch).
+  // Treat as transient regardless of nested cause code because causes vary
+  // across runtimes and can be unclassified even for real network faults.
   if (err instanceof TypeError && err.message === "fetch failed") {
-    const cause = getErrorCause(err);
-    if (cause) {
-      return isTransientNetworkError(cause);
-    }
     return true;
   }