Update contributing, deduplicate more functions

src/agents/pi-embedded-runner/abort.ts

@@ -1 +1,17 @@
-export { isAbortError } from "../../infra/unhandled-rejections.js";
+/**
+ * Runner abort check. Catches any abort-related message for embedded runners.
+ * More permissive than the core isAbortError since runners need to catch
+ * various abort signals from different sources.
+ */
+export function isRunnerAbortError(err: unknown): boolean {
+  if (!err || typeof err !== "object") {
+    return false;
+  }
+  const name = "name" in err ? String(err.name) : "";
+  if (name === "AbortError") {
+    return true;
+  }
+  const message =
+    "message" in err && typeof err.message === "string" ? err.message.toLowerCase() : "";
+  return message.includes("aborted");
+}