#15422: fix(auto-reply): keep cron systemEvent payloads that start with 'Read HEARTBEAT.md'

## Summary - stop dropping system events just because text starts with `Read HEARTBEAT.md` - keep existing heartbeat poll/wake noise filtering unchanged - add regression tests to ensure user cron payloads with this prefix are preserved ## Why `compactSystemEvent()` used a text-prefix heuristic that filtered legitimate user-configured cron payloads (issue #15399). ## Testing - `pnpm --dir /root/clawd/work/openclaw exec vitest run src/auto-reply/reply/session-resets.test.ts` - `pnpm --dir /root/clawd/work/openclaw exec vitest run src/infra/system-events.test.ts` Fixes #15399 <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This change adjusts `prependSystemEvents` to stop dropping queued system events purely because their text starts with `Read HEARTBEAT.md`, while keeping the existing filtering for heartbeat poll/wake noise. In context, cron jobs enqueue their payloads into the system-events queue (see `src/gateway/server-cron.ts`), and `prependSystemEvents` is responsible for prefixing that queue into the next prompt. The added regression tests assert that user-configured cron payloads starting with `Read HEARTBEAT.md` are preserved, and that poll/wake noise continues to be removed. <h3>Confidence Score: 5/5</h3> - This PR is safe to merge with minimal risk. - The change is a narrow removal of an over-broad text-prefix filter in `prependSystemEvents`, and tests cover both the regression case and preservation of existing heartbeat poll/wake filtering. Heartbeat prompting itself is handled via the heartbeat runner as a user message, so preserving system events that start with `Read HEARTBEAT.md` aligns with current architecture. - No files require special attention _{Last reviewed commit: a090aed} <!-- greptile_other_comments_section --> <!-- /greptile_comment -->