fix(skills): evidence-based prompt delivery (send_keys_safe) to end prompt-lock (FW-W2)

- Add send_keys_safe + quiescence/dialog-detection helpers to lib.sh:
  keys are sent on pane evidence, never fixed timers; distinct exit
  codes 1-4; dialogs are never blindly Enter-ed
- inject_instructions delegates to send_keys_safe; create --submit-job
  publishes a terminal error event on delivery failure (no zombie jobs)
- wait_for_tui_ready: drop dialog-ambiguous tokens, treat open dialogs
  as not-ready, return 1 on timeout instead of proceeding
- delegate-job wrapper: replace copy-pasted raw paste/C-m block with
  lib.sh send_keys_safe (restores single source of truth)
- resume: conditional signature-gated dialog handling replaces blind
  Enter/Down/Enter; stop --graceful delivers exitkey safely, fallback
  chain unchanged
- create SKILL: passive capture-pane probe instead of stray Enter
- Mark FW-W2 resolved; add 3-agent analysis/plan reports

.agents/skills/multi-agent-mux-stop/scripts/stop_session.sh

@@ -189,7 +189,7 @@ graceful_stop() {
     *)      exitkey="/exit" ;;
   esac
   echo "graceful: send-keys '$exitkey' to $SESSION_NAME"
-  tmux send-keys -t "$SESSION_NAME" "$exitkey" Enter 2>/dev/null || true
+  send_keys_safe "$SESSION_NAME" "$exitkey" "stop$$" || echo "graceful: safe delivery failed (rc=$?) — falling back to kill chain"
   sleep 3
   if ! tmux has-session -t "$SESSION_NAME" 2>/dev/null; then
     echo "graceful: exited cleanly"