feat: add business hours scheduling to heartbeat

- Configurable start/end hours (0-23)
- Timezone support (default: UTC)
- Silent skip outside business hours (no log spam)
- Backward compatible (no schedule = always run)

lib/services/heartbeat.ts

@@ -31,6 +31,13 @@ export type HeartbeatConfig = {
   enabled: boolean;
   intervalSeconds: number;
   maxPickupsPerTick: number;
+  schedule?: {
+    enabled_hours?: {
+      start: number; // 0-23
+      end: number;   // 0-23
+      timezone?: string; // IANA timezone (default: UTC)
+    };
+  };
 };
 
 type Agent = {
@@ -165,6 +172,26 @@ function hasProjects(workspace: string): boolean {
   );
 }
 
+/**
+ * Check if current time is within enabled hours.
+ */
+function isWithinBusinessHours(config: HeartbeatConfig): boolean {
+  if (!config.schedule?.enabled_hours) return true;
+
+  const { start, end, timezone = "UTC" } = config.schedule.enabled_hours;
+  
+  // Get current hour in the configured timezone
+  const now = new Date();
+  const formatter = new Intl.DateTimeFormat("en-US", {
+    timeZone: timezone,
+    hour: "numeric",
+    hour12: false,
+  });
+  const currentHour = parseInt(formatter.format(now), 10);
+
+  return currentHour >= start && currentHour < end;
+}
+
 /**
  * Run one heartbeat tick for all agents.
  */
@@ -174,6 +201,11 @@ async function runHeartbeatTick(
   pluginConfig: Record<string, unknown> | undefined,
   logger: ServiceContext["logger"],
 ): Promise<void> {
+  // Skip tick if outside business hours
+  if (!isWithinBusinessHours(config)) {
+    return; // Silent skip - no logging spam
+  }
+
   try {
     const result = await processAllAgents(agents, config, pluginConfig, logger);
     logTickResult(result, logger);