fix: skip heartbeat when HEARTBEAT.md does not exist (#20461)

Merged via /review-pr -> /prepare-pr -> /merge-pr.

Prepared head SHA: f6e5f8172a
Co-authored-by: vikpos <24960005+vikpos@users.noreply.github.com>
Co-authored-by: gumadeiras <5599352+gumadeiras@users.noreply.github.com>
Reviewed-by: @gumadeiras

src/infra/heartbeat-reason.ts

@@ -0,0 +1,54 @@
+export type HeartbeatReasonKind =
+  | "retry"
+  | "interval"
+  | "manual"
+  | "exec-event"
+  | "wake"
+  | "cron"
+  | "hook"
+  | "other";
+
+function trimReason(reason?: string): string {
+  return typeof reason === "string" ? reason.trim() : "";
+}
+
+export function normalizeHeartbeatWakeReason(reason?: string): string {
+  const trimmed = trimReason(reason);
+  return trimmed.length > 0 ? trimmed : "requested";
+}
+
+export function resolveHeartbeatReasonKind(reason?: string): HeartbeatReasonKind {
+  const trimmed = trimReason(reason);
+  if (trimmed === "retry") {
+    return "retry";
+  }
+  if (trimmed === "interval") {
+    return "interval";
+  }
+  if (trimmed === "manual") {
+    return "manual";
+  }
+  if (trimmed === "exec-event") {
+    return "exec-event";
+  }
+  if (trimmed === "wake") {
+    return "wake";
+  }
+  if (trimmed.startsWith("cron:")) {
+    return "cron";
+  }
+  if (trimmed.startsWith("hook:")) {
+    return "hook";
+  }
+  return "other";
+}
+
+export function isHeartbeatEventDrivenReason(reason?: string): boolean {
+  const kind = resolveHeartbeatReasonKind(reason);
+  return kind === "exec-event" || kind === "cron" || kind === "wake" || kind === "hook";
+}
+
+export function isHeartbeatActionWakeReason(reason?: string): boolean {
+  const kind = resolveHeartbeatReasonKind(reason);
+  return kind === "manual" || kind === "exec-event" || kind === "hook";
+}