fix: heartbeat prompt + dedupe (#980) (thanks @voidserf)

- tighten default heartbeat prompt guidance
- suppress duplicate heartbeat alerts within 24h

Co-authored-by: void <voidserf@users.noreply.github.com>

src/config/sessions/types.ts

@@ -10,6 +10,13 @@ export type SessionChannelId = ChannelId | "webchat";
 export type SessionChatType = "direct" | "group" | "room";
 
 export type SessionEntry = {
+  /**
+   * Last delivered heartbeat payload (used to suppress duplicate heartbeat notifications).
+   * Stored on the main session entry.
+   */
+  lastHeartbeatText?: string;
+  /** Timestamp (ms) when lastHeartbeatText was delivered. */
+  lastHeartbeatSentAt?: number;
   sessionId: string;
   updatedAt: number;
   sessionFile?: string;

src/config/types.agent-defaults.ts

@@ -163,7 +163,7 @@ export type AgentDefaultsConfig = {
       | "none";
     /** Optional delivery override (E.164 for WhatsApp, chat id for Telegram). */
     to?: string;
-    /** Override the heartbeat prompt body (default: "Read HEARTBEAT.md if exists. Consider outstanding tasks. Checkup sometimes on your human during (user local) day time."). */
+    /** Override the heartbeat prompt body (default: "Read HEARTBEAT.md if it exists (workspace context). Follow it strictly. Do not infer or repeat old tasks from prior chats. If nothing needs attention, reply HEARTBEAT_OK."). */
     prompt?: string;
     /** Max chars allowed after HEARTBEAT_OK before delivery (default: 30). */
     ackMaxChars?: number;