[Bug] Version 2.1.243 fails to launch on multiple machines, autoupdate causes regression

**Bug Description**
claude code 2.1.243 is broken on all of my machines, i can only launch Claude Code if i revert to 2.1.241 but then autoupdate puts me right back in the same predicament. claude update, claude doctor, claude, all fail. Not even a fresh install resolves the issue. The only way I found to avoid this trap is to block autoupdate.

**Environment Info**
- Platform: linux
- Terminal: ghostty
- Version: 2.1.241
- Feedback ID: ec9ae07b-920b-478a-8316-0ae44b902ef1

**Errors**
```json
fish: Job 1, 'claude' terminated by signal SIGSEGV (Address boundary error)
```

Reproduce the failure on Linux with fish by comparing Claude Code 2.1.243 against 2.1.241, including the claude, claude update, and claude doctor entry points. Trace the autoupdate path and startup failure; done means a fresh install launches, update and doctor complete, and autoupdate no longer returns the installation to the SIGSEGV regression.

Written by the indexing model from the issue text.