fix(reset): refuse id-less claude/grok targets, gate submit during a reset, validate the spec (#78)

Review round 1 of PR #82:
- A running claude/grok row without a recorded id is refused by the
  precheck (stop would fill it with a folder-wide guess the purge then
  deletes); record-id never records a pre-assigned guess, and a target is
  skipped (id_unverified) when the row's id after the normal stop is not
  the one recorded before it.
- reset takes the update admission lock exclusively while it publishes
  .mam/loop-guard-active and .mam/reset-in-progress; delegate submit
  refuses on a live reset marker (mam_reset_admit). Before each target's
  stop its open jobs are re-read (skipped as open_job, never cancelled),
  and a row whose agent/server no longer matches the spec is skipped.
- read_spec validates every stored field (herdr_server required, never
  defaulted) and rejects duplicate names.
- Signal tests wait 60 s for the kill-session gate (this Mac needs ~18 s).

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

.agents/skills/multi-agent-mux-delegate-job/multi-agent-mux-delegate-job

@@ -306,7 +306,8 @@ cmd_submit() {
   # its row's, or with no row the live agent's on the server delivery uses)
   # runs; each is held, fd 7 then 20.., until the record is written (lib.sh
   # mam_update_admit). A dry-run record is never dispatched and is not
-  # counted by the update.
+  # counted by the update. Issue #78: likewise while a reset of one runs
+  # (mam_reset_admit, checked under the same admission).
   local admit_fds=() target_ws tws fd=20
   if [[ "$DRY_RUN" != "1" ]]; then
     target_ws="$(MAM_STATE_JSON="$(load_state_json)" PYTHONPATH="$SKILL_DIR:${PYTHONPATH:-}" "$PY" -m lib_py.update \
@@ -315,9 +316,11 @@ cmd_submit() {
       --herdr "$(_resolve_real_herdr_path || true)")" \
       || { echo "ERROR: cannot resolve the workspace of $AGENT_SESSION; nothing was registered" >&2; exit 1; }
     mam_update_admit "$WORKSPACE_ROOT" || exit 1
+    mam_reset_admit "$WORKSPACE_ROOT" || exit 1
     while IFS= read -r tws; do
       [[ -n "$tws" ]] || continue
       mam_update_admit "$tws" "$fd" || exit 1
+      mam_reset_admit "$tws" || exit 1
       admit_fds+=("$fd"); fd=$((fd + 1))
     done <<< "$target_ws"
   fi