fix(coordination): move WatchError import to top of shared_runtime_bag.py #8707

Problem

In autobot_shared/coordination/shared_runtime_bag.py, WatchError is imported inside the except block of the CAS retry loop:

except Exception as exc:
    from redis.exceptions import WatchError   # re-imported on every failed attempt
    if not isinstance(exc, WatchError):
        raise

This re-evaluates the import on every CAS failure. Move to top-of-file.

Fix

Add to module-level imports:

from redis.exceptions import WatchError

Remove the inline import.

Discovery

Found during CodeReviewer review of PR #8693 / GH#6630.