Gap 1: a thread with a persisted sandbox_id but no in-memory cache and no
recorded bound_repo (a pre-binding legacy thread, post-deploy) previously
reconnected-and-served the sandbox to the current repo, then rebound it. Now
fail closed: drop the stale id and recreate a fresh sandbox bound to this repo,
logging a reconnect-with-missing-binding event. A sandbox is never served to a
repo unless its binding is known and matches; new threads bind on first run
unchanged.
Gap 3: catch SandboxRepoMismatchError at the agent and reviewer run entrypoints,
log it for alarming, and surface a clean sanitized error instead of letting an
opaque deep-stack exception crash-loop the worker.