fix(rerun): preserve exit code and escalate auth errors in batch rerun (#33)

pollAccepted in runTestRerun hardcoded exitCode:1 on ApiError, causing
the auth-escalation find(r => r.error?.exitCode === 3) to always return
undefined -- auth failures silently exited 1 instead of 3.

- preserve err.exitCode in pollAccepted (mirrors runTestRunAll fix)
- add auth escalation block before generic exit-1 throw
- bound initial chunk idempotency key to <=256 chars (mirrors retry path)

Author: crypticsaiyan