fix(lib.sh): one herdr name rule; the shim's agent attach resolves its target (Issue #71)

- One _sanitize_herdr_agent_name: the shim gets lib.sh's definition through
  `declare -f` instead of a second copy. Without shasum/sha1sum/openssl it
  hashes with python3 (same result as lib_py.agents.sanitize); with none of
  them it fails instead of truncating or appending 00000000.
- Every caller stops on that failure: new-session before any pane is made,
  the lookups report failure, and has-session takes the name lib.sh computed
  (the cwd-relative import and its lower()[:32] fallback are gone).
- `herdr agent attach <name>` through the shim resolves the target like
  get/read/prompt; options after the target are kept.

Refs #71

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

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

@@ -895,8 +895,8 @@ finalize_unfinished() {
   FINAL_JOB_STATUS="$final"
   if [ "$step" = "probe" ]; then
     local sess="${target_sess#herdr:}" target_agent diag="no"
-    target_agent=$(_sanitize_herdr_agent_name "$sess")
-    _within_deadline "$deadline" _agent_still_working "$sess" "$target_agent" && diag="yes"
+    target_agent=$(_sanitize_herdr_agent_name "$sess") || target_agent=""
+    [ -n "$target_agent" ] && _within_deadline "$deadline" _agent_still_working "$sess" "$target_agent" && diag="yes"
     echo "liveness: no wire event for ${IDLE_TIMEOUT}s on job $job_id; herdr/pane says busy=$diag (diagnostic only, not evidence)" >&2
   fi
   # The answer comes back on fd 3: stdout carries registry.py's close output.