fix: address round 2 review findings from issue #81

- Move atomic mv inside gardener loop so reply is only claimed when a
  matching needs_human session exists (fixes reply-loss regression)
- Delay rm of claimed file until after successful injection in both
  supervisor and gardener (OOM/SIGKILL leaves file recoverable)
- Fix matrix_listener ack message: 'next poll' instead of 'next supervisor poll'

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

supervisor/supervisor-poll.sh

@@ -540,7 +540,6 @@ check_project() {
     _nh_claimed="/tmp/dev-escalation-reply.supervisor.$$"
     if [ -s "$HUMAN_REPLY_FILE" ] && mv "$HUMAN_REPLY_FILE" "$_nh_claimed" 2>/dev/null; then
       _nh_reply=$(cat "$_nh_claimed")
-      rm -f "$_nh_claimed"
       _nh_inject_msg="Human reply received for issue #${_nh_issue}:
 
 ${_nh_reply}
@@ -558,7 +557,7 @@ Instructions:
       sleep 0.5
       tmux send-keys -t "$_nh_session" "" Enter || true
       tmux delete-buffer -b "human-inject-${_nh_issue}" 2>/dev/null || true
-      rm -f "$_nh_tmpfile"
+      rm -f "$_nh_tmpfile" "$_nh_claimed"
 
       rm -f "/tmp/dev-renotify-${proj_name}-${_nh_issue}"
       flog "${proj_name}: #${_nh_issue} human reply injected into session ${_nh_session}"