Reliable loop messaging: msg-loop.sh + hardened ping_session (retry submit)

tmux `send-keys -l <long msg>` often leaves the text UNSENT in the input box (the
immediate Enter is swallowed while the TUI ingests the paste). Both now type the
message then retry Enter/C-m until the leading text is no longer in the input box
(= submitted) or a bounded loop gives up.
- msg-loop.sh: standalone reliable messenger for orchestrator use.
- launch.sh ping_session: same retry-submit (loads on next watchdog restart).
Live-tested: delivered first try.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

cc-ci-plan/msg-loop.sh

@@ -0,0 +1,33 @@
+#!/usr/bin/env bash
+# msg-loop.sh — reliably send a message to a loop's tmux session AND submit it.
+# -------------------------------------------------------------------------
+# `tmux send-keys -l <long message>` frequently leaves the text sitting UNSENT in
+# the input box (the immediate Enter is swallowed while the TUI is still ingesting
+# the paste). This types the message, then retries Enter/C-m until the text is no
+# longer in the input box (= it was submitted), or gives up after a bounded loop.
+#
+#   msg-loop.sh <tmux-session> <message...>
+# exit 0 = delivered; 2 = could not confirm submit; 1 = bad args / no session.
+set -uo pipefail
+
+S="${1:?usage: msg-loop.sh <session> <message...>}"; shift
+MSG="$*"
+[ -n "$MSG" ] || { echo "msg-loop: empty message"; exit 1; }
+tmux has-session -t "$S" 2>/dev/null || { echo "msg-loop: no tmux session '$S'"; exit 1; }
+
+PREFIX="$(printf '%s' "$MSG" | head -c 28)"
+# Submitted ⇔ the message's leading text is no longer in the input box (bottom of the pane).
+in_input_box() { tmux capture-pane -pt "$S" 2>/dev/null | tail -4 | grep -qF -- "$PREFIX"; }
+
+tmux send-keys -t "$S" -l -- "$MSG" 2>/dev/null || { echo "msg-loop: send-keys failed"; exit 1; }
+sleep 0.8
+for _ in 1 2 3 4 5 6 7 8 9 10; do
+  tmux send-keys -t "$S" Enter 2>/dev/null || true
+  sleep 1.2
+  in_input_box || { echo "$S: delivered ✔"; exit 0; }
+  tmux send-keys -t "$S" C-m 2>/dev/null || true   # some TUI states take C-m not Enter
+  sleep 0.8
+  in_input_box || { echo "$S: delivered ✔"; exit 0; }
+done
+echo "$S: WARNING — could not confirm submit; message may remain in the input box"
+exit 2