feat: update heartbeat defaults

src/auto-reply/heartbeat.ts

@@ -1,8 +1,15 @@
 import { HEARTBEAT_TOKEN } from "./tokens.js";
 
-export const HEARTBEAT_PROMPT = "HEARTBEAT";
+export const HEARTBEAT_PROMPT =
+  "Read HEARTBEAT.md if exists. Consider outstanding tasks. Checkup sometimes on your human during (user local) day time.";
+export const DEFAULT_HEARTBEAT_EVERY = "30m";
 export const DEFAULT_HEARTBEAT_ACK_MAX_CHARS = 30;
 
+export function resolveHeartbeatPrompt(raw?: string): string {
+  const trimmed = typeof raw === "string" ? raw.trim() : "";
+  return trimmed || HEARTBEAT_PROMPT;
+}
+
 export type StripHeartbeatMode = "heartbeat" | "message";
 
 function stripTokenAtEdges(raw: string): { text: string; didStrip: boolean } {