Decision 8: delegate submit uses the admission lock of the workspace the
target session belongs to. The wrapper resolved only its own
WORKSPACE_ROOT, so a job could be registered and delivered to an agent of
another installed workspace while that workspace was being updated.
lib_py.update target-workspace resolves a herdr:<name> row's workspace (the
.mam at or above its pane.cwd, else its control_plane.workspace_root);
mam_update_admit takes an fd, and submit holds the caller root on fd 7 and
the target on fd 8 until the record is written. Rowless and remote targets
keep the caller-root gate.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>