#22424: fix: prevent crash when onUpdate is truthy but not callable (fixes #22206)

## Summary Fixes #22206 — prevents gateway crash when `opts.onUpdate` is truthy but not a function during exec runtime. ## Problem The crash occurred during boot-md gateway startup when: 1. Embedded agent run starts 2. Skills-remote probe times out 3. Supervisor stdout handler fires `emitUpdate()` after the `onUpdate` callback has been invalidated 4. The guard at line 335 used `if (!opts.onUpdate)` — a falsy check that doesn't catch truthy non-functions like `true` or `{}` 5. Line 340 attempts to call `opts.onUpdate({...})` → TypeError ## Root Cause Analysis After extensive investigation, I could not find explicit code that sets `onUpdate` to `true` or `{}`. The issue appears to occur during race conditions in cleanup/teardown scenarios where: - The process continues running and generating stdout - The callback has been invalidated (possibly during abort/timeout/cleanup) - But stdout arrives after invalidation ## History This bug was introduced in b47fa9e71 (about 2 months ago) but remained latent until PR #20569 merged. That PR changed boot-md to run per-agent, significantly increasing the probability of hitting this race condition during gateway startup. ## Solution Changed the guard from falsy check to typeof check: ```diff - if (!opts.onUpdate) return; + if (typeof opts.onUpdate !== "function") return; ``` This is a defensive fix that prevents the crash regardless of how the callback becomes invalid. The trade-off (lost progress updates when callback is invalidated) is acceptable compared to the crash (restart loop until stale locks clear). ## Test Plan - [x] Added regression tests in `bash-tools.exec-runtime.guard.test.ts` - [x] Tests reproduce the crash with `onUpdate: true` and `onUpdate: {}` - [x] Tests verify the fix prevents the crash - [x] CI gate passed (pnpm build && pnpm check) ## Impact - Eliminates restart loop on gateway startup when boot-md encounters timeouts - No functional changes to normal operation (guard only triggers when callback is already corrupted) <!-- greptile_comment --> <h3>Greptile Summary</h3> This PR fixes a crash in the bash exec runtime that occurred when `onUpdate` callback was truthy but not callable. The fix changes the guard from a falsy check (`if (!opts.onUpdate)`) to a proper type check (`if (typeof opts.onUpdate !== "function")`), preventing `TypeError` when the callback becomes invalidated during race conditions in cleanup/teardown scenarios. - Fixed critical crash bug in `bash-tools.exec-runtime.ts:335` affecting gateway startup - Added comprehensive regression tests covering `onUpdate: true` and `onUpdate: {}` scenarios - Aligns with existing codebase patterns (27+ other `typeof ... !== "function"` checks found) - Other file changes are formatting-only (import order via `oxfmt`) <h3>Confidence Score: 5/5</h3> - This PR is safe to merge with minimal risk - The fix is a minimal, defensive guard change that prevents a crash without altering any functional behavior. The typeof check aligns with 27+ existing patterns in the codebase. Comprehensive regression tests verify the fix prevents the crash scenarios. The only substantive change is a single-line guard improvement; other changes are formatting-only. - No files require special attention _{Last reviewed commit: 1712851} <!-- greptile_other_comments_section --> <!-- /greptile_comment -->