#23726: fix(resilience): destroy write streams on download errors

## Summary - Problem: Write streams created during media downloads and signal-cli installation are not explicitly destroyed on error paths (size limit exceeded, pipeline failure), potentially leaving file handles open - Why it matters: Leaked file handles can accumulate over time, leading to EMFILE errors or inaccessible temporary files - What changed: Added explicit `out.destroy()` calls on error paths in media store download and signal-cli installer - What did NOT change: Happy-path download behavior is identical ## Change Type - [x] Bug fix ## Scope - [x] Gateway / orchestration - [x] Integrations ## Security Impact - New permissions/capabilities? No - Secrets/tokens handling changed? No - New/changed network calls? No - Command/tool execution surface changed? No - Data access scope changed? No 🤖 Generated with [Claude Code](https://claude.com/claude-code) <!-- greptile_comment --> <h3>Greptile Summary</h3> Added `out.destroy()` calls to properly clean up write streams when download errors occur in both media store and signal-cli installer. - `src/commands/signal-install.ts`: Complete fix with both stream destruction and file cleanup via `fsUnlink` - `src/media/store.ts`: Only added stream destruction on size limit exceeded path, missing file cleanup on pipeline failure The fix in `signal-install.ts` is complete and follows the correct pattern. However, `store.ts` needs the same file cleanup pattern in the pipeline catch handler (line 196) to prevent leaked partial files when downloads fail. <h3>Confidence Score: 3/5</h3> - This PR partially addresses the file handle leak issue but leaves one error path without proper cleanup - The fix correctly addresses the write stream cleanup issue in `signal-install.ts` with both `out.destroy()` and file cleanup. However, `store.ts` only adds `out.destroy()` on the size limit check but doesn't clean up the partial file in the pipeline catch handler, creating an incomplete fix that still allows file leaks on download errors - Pay close attention to `src/media/store.ts` - the pipeline catch handler needs file cleanup logic _{Last reviewed commit: c748aff} <!-- greptile_other_comments_section --> <!-- /greptile_comment -->