fix(delegate): admission covers a rowless target and the installed parent of an incidental .mam (Issue #72, review round 2)

R1: a target with no registry row skipped the target gate. Its cwd is now
read from the live agent on the server delivery uses (resolve_herdr_session),
through the real herdr only when that server is running, so no server is
started; a herdr that cannot answer refuses before registration.

R2: any .mam counted as a workspace and stopped the walk, so B/sub/.mam hid
an installed B and the row's control_plane root was dropped. Workspaces are
now update.sh's installed trees (.mam_deploy/remove.sh or remove.sh): every
installed ancestor of the cwd, plus the recorded control_plane root.

lib_py.update target-workspaces prints them one per line; the wrapper holds
each on fds 20.. until the record is written.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.agents/skills/lib.sh

@@ -3266,7 +3266,7 @@ mam_control_plane_prefix() {
 #
 # mam_update_admit [workspace [fd]]: rc 0 admitted (fd 7, or the given one,
 # held unless the workspace has no .mam), 1 refused (stderr). Delegate submit
-# also takes its target's workspace on fd 8.
+# also takes the workspaces its target is in on fds 20 and up.
 mam_update_admit() {
   local root="${1:-$WORKSPACE_ROOT}" fd="${2:-7}"
   local lock="$root/.mam/update-admission.lock" marker="$root/.mam/update-in-progress" st