Review round 3 R1 (codex): the registration guard chose the workspace marker
from the path's spelling, so a symlink alias of .mam/jobs or a MAM_JOBS_DIR
registry was not refused. The reset now writes .reset-in-progress into each
registry its open-job check reads (.mam/jobs, MAM_JOBS_DIR, a row's other
control_plane.mam_jobs_dir - the latter only for this workspace's sessions),
each under that registry's lock and before the check, and removes it on exit;
register_job reads the marker inside the registry it writes to. The
precheck's separate lock barrier is subsumed by the fence.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>