* feat: improve spawn error handling and reporting across full stack
- Return error result instead of throwing in apiMachine spawn handler
- Add lastSpawnError field to RunnerState for persistent error tracking
- Add error awaiter system for early process exit/error detection before webhook
- Build detailed webhook failure messages with exit code, signal, and stderr tail
- Report spawn outcomes to hub via runner state updates
- Handle more spawn result types in rpcGateway with better error messages
- Display runner last spawn error in web UI (NewSession & SpawnSession)
- Extract shared formatRunnerSpawnError utility to avoid duplication
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
* fix(cli): narrow spawnResult type check to fix TS2339 error
Use `type === 'error'` instead of `type !== 'success'` to properly
narrow the discriminated union, allowing TypeScript to infer errorMessage.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
