The respawn runs with the session map unlocked, so two takes of the
lock straddle it. A kill landing in that window deleted the sidecar
before resume wrote it back, leaving a file for a session that was
gone — the next recovery registered it as a dormant ghost. Resume now
deletes the sidecar in the branch where it finds its own record gone.
Two resumes both passed the `Running` check for the same reason. The
record is marked in-flight under the first lock, so the second request
is refused with `already_running` instead of losing a race for the
FIFO and reporting a tmux failure. Every path out of resume clears the
marker.
Both races are driven deterministically in the tests: the manager's
tmux spawn is parked mid-resume while the racing kill or resume runs.
Closes#175
Miguel Palhas
ae3091e2a2