#17823: fix: memory leak in cron isolated runs — agent-events Maps never cleaned (#17820)

Fixes #17820 ## Problem Cron isolated agent runs leak memory through two unbounded Maps in `src/infra/agent-events.ts`: 1. **`seqByRun`** — grows with every agent run but `clearAgentRunContext()` only deletes from `runContextById`, not `seqByRun`. Affects all runs (interactive + cron). 2. **`runContextById`** — `clearAgentRunContext()` is called from `server-chat.ts` for interactive sessions but never from the cron code path (`src/cron/isolated-agent/run.ts`). With frequent cron jobs (e.g., 5-min intervals), the gateway leaks ~1-2GB over 10-12 hours. ## Fix **`src/infra/agent-events.ts`:** Add `seqByRun.delete(runId)` to `clearAgentRunContext()` so both Maps are cleaned. **`src/cron/isolated-agent/run.ts`:** Import `clearAgentRunContext` and call it in `withRunSession()` — the single exit point for all cron run results — ensuring cleanup happens on every path (success, error, skipped). ## Testing Verified on a production instance running 9 cron jobs. Before fix: memory grew from ~500MB to 1.9GB+ swap in 10h. After fix: memory stable at ~500MB over equivalent period. <!-- greptile_comment --> <h3>Greptile Summary</h3> Fixes a memory leak where two module-level Maps (`seqByRun` and `runContextById`) in `src/infra/agent-events.ts` grew unboundedly during cron isolated agent runs. The fix is minimal and correct: - `clearAgentRunContext()` now deletes from both `seqByRun` and `runContextById` (previously only cleaned `runContextById`). - The cron code path (`src/cron/isolated-agent/run.ts`) now calls `clearAgentRunContext()` inside `withRunSession()` — the single exit point for all cron run results after context registration — ensuring cleanup on every path (success, error, skipped). All return paths after `registerAgentRunContext` (line 412) flow through `withRunSession`, and the one early return (line 225) occurs before any context is registered, so no cleanup is needed there. The interactive path in `server-chat.ts` was already calling `clearAgentRunContext` correctly. <h3>Confidence Score: 5/5</h3> - This PR is safe to merge — it adds targeted cleanup calls with no behavioral side effects. - The changes are minimal, well-scoped, and correct. Both Maps are now cleaned in `clearAgentRunContext`, and the cron exit path reliably calls it. The fix matches the existing pattern used in `server-chat.ts` and `commands/agent.ts`. Production validation confirms the leak is resolved. - No files require special attention. _{Last reviewed commit: 7a0b7c4} <!-- greptile_other_comments_section --> <!-- /greptile_comment -->