Eng-review finding: getClaudeCliVersion's fallback is a SYNCHRONOUS
spawnSync on the same thread that polls concurrent PTY/session tests — the
judgePtyState blocking class this overhaul kills elsewhere. The paid runner
parent now resolves it once (cached) and stamps GSTACK_CLAUDE_CLI_VERSION
into every shard's env; eval-store short-circuits on the env var, and the
fallback spawn's budget tightens 10s -> 3s (bounded one-time stall, records
'unknown' on a slow CLI).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>