fix(framework): send-message.sh fail-loud submission verdict + regression tests (Patch 6)

Invert the delivery verdict from negative to positive evidence. Previously,
success was declared by the ABSENCE of a draft snippet on a prompt line: if
the `❯|^>|│ >` glyph matched nothing (busy-receiver draft on an unmatched
line, or wrong-pane drift), an UNSUBMITTED message read as "✓ delivered"
exit 0 — a silent worker->lead relay stall (filed by UC-LEAD, PR #3046:
three review verdicts reported delivered but never surfaced for ~50 min).

Fix: success now requires POSITIVE evidence — either the queued banner, or
the REPL input box located AND clear of the message tail. If the input box
cannot be located, status is `unconfirmed` -> exit 2 + stderr ("could not
confirm submission ... may be UNDELIVERED"). The near-dead `*)` indeterminate
default also flips from silently returning 0 to exit 2. Bracketed-paste and
double-Enter delivery mechanics are unchanged; queued/draft/delivered
semantics are preserved, only the failure-mode default direction changes.

Adds `test-send-message-verdict.sh`: 3 real tmux-pane fixtures (delivered /
unconfirmed-glyphless / draft) locking the fail-loud verdict logic, and
upgrades `test-send-message-socket.sh` fixtures from a glyphless bash prompt
to `❯`-prompt REPLs so the patched binary can read delivery positively.

Reproduce-first evidence (baseline vs patched, glyphless-pane fixture):
  baseline: rc=0, stdout "✓ delivered to =noglyph" (silent false positive)
  patched:  rc=2, stderr "could not confirm submission ... may be UNDELIVERED"

Test results after port:
  test-send-message-verdict.sh -> PASS=3 FAIL=0
  test-send-message-socket.sh  -> ok

Firewall: grep -niE 'jason|woltje|jarvis' on changed files = 0 hits;
tools/quality/scripts/verify-sanitized.sh -> sanitization gate passed.
shellcheck: 1 pre-existing SC2034 finding (unused loop var `attempt`,
present identically in baseline) carried through; 0 new findings.

Part of #891

packages/mosaic/framework/tools/tmux/test-send-message-verdict.sh

@@ -0,0 +1,74 @@
+#!/usr/bin/env bash
+# test-send-message-verdict.sh — locks the fail-loud verdict logic of the patched
+# send-message.sh against three real tmux-pane fixtures on a throwaway socket:
+#
+#   1. DELIVERED   — a REPL that renders a `❯ ` input box and submits on Enter
+#                    (text scrolls to history, box clears) => exit 0 "✓ delivered".
+#   2. UNCONFIRMED — a pane with NO locatable prompt glyph. This is the exact
+#                    historical FALSE POSITIVE: pre-patch it printed "✓ delivered"
+#                    exit 0; post-patch it MUST fail loud (exit 2, stderr
+#                    "could not confirm submission").
+#   3. DRAFT       — a `❯ `-prompt pane that never submits (message stays on the
+#                    input line) => exit 2, stderr "unsubmitted draft".
+set -uo pipefail
+
+HERE=$(cd -- "$(dirname -- "$0")" && pwd)
+SEND="$HERE/send-message.sh"
+SOCKET="verdict-test-$RANDOM-$$"
+TMP=$(mktemp -d)
+trap 'tmux -L "$SOCKET" kill-server >/dev/null 2>&1 || true; rm -rf "$TMP"' EXIT
+
+PASS=0; FAIL=0
+ok() { PASS=$((PASS+1)); printf '  ok   %s\n' "$1"; }
+no() { FAIL=$((FAIL+1)); printf '  FAIL %s\n       %s\n' "$1" "$2"; }
+
+command -v tmux >/dev/null 2>&1 || { echo "tmux required" >&2; exit 1; }
+
+# --- Fixture 1: a submitting REPL with a ❯ prompt box (interactive bash, glyph PS1).
+#     readline strips bracketed-paste markers just like a real agent REPL; Enter
+#     executes (text -> scrollback), leaving a fresh empty `❯ ` box.
+tmux -L "$SOCKET" new-session -d -s repl -c "$TMP" \
+  'PS1="❯ " exec bash --noprofile --norc -i'
+sleep 0.3
+out=$("$SEND" -L "$SOCKET" -t "=repl" -m "verdict fixture one delivered ok" 2>"$TMP/e1"); rc=$?
+if [ "$rc" -eq 0 ] && printf '%s' "$out" | grep -qF "✓ delivered"; then
+  ok "delivered: ❯-prompt REPL that submits => exit 0 ✓ delivered"
+else
+  no "delivered: ❯-prompt REPL that submits => exit 0 ✓ delivered" "rc=$rc out=[$out] err=[$(cat "$TMP/e1")]"
+fi
+
+# --- Fixture 2: NO prompt glyph (default bash PS1). THE regression: pre-patch this
+#     was a silent false-positive "delivered"; post-patch it must be unconfirmed→exit 2.
+tmux -L "$SOCKET" new-session -d -s noglyph -c "$TMP" \
+  'PS1="sh-noglyph$ " exec bash --noprofile --norc -i'
+sleep 0.3
+if out=$("$SEND" -L "$SOCKET" -t "=noglyph" -m "verdict fixture two must fail loud" 2>"$TMP/e2"); then
+  no "unconfirmed: glyphless pane must NOT report success" "expected exit 2, got 0 (out=[$out])"
+else
+  rc=$?
+  if [ "$rc" -eq 2 ] && grep -qF "could not confirm submission" "$TMP/e2"; then
+    ok "unconfirmed: glyphless pane => exit 2 + 'could not confirm submission' (false-positive FIXED)"
+  else
+    no "unconfirmed: glyphless pane => exit 2 + stderr" "rc=$rc err=[$(cat "$TMP/e2")]"
+  fi
+fi
+
+# --- Fixture 3: a ❯ box that never submits (sleep ignores stdin; TTY echo keeps the
+#     pasted tail sitting on the ❯ line) => draft => exit 2.
+tmux -L "$SOCKET" new-session -d -s draft -c "$TMP" \
+  'printf "❯ "; exec sleep infinity'
+sleep 0.3
+if out=$("$SEND" -L "$SOCKET" -t "=draft" -r 1 -m "verdict fixture three stuck unsubmitted draft" 2>"$TMP/e3"); then
+  no "draft: unsubmitted message must NOT report success" "expected exit 2, got 0 (out=[$out])"
+else
+  rc=$?
+  if [ "$rc" -eq 2 ] && grep -qF "unsubmitted draft" "$TMP/e3"; then
+    ok "draft: stuck ❯-line message => exit 2 + 'unsubmitted draft'"
+  else
+    no "draft: stuck ❯-line message => exit 2 + stderr" "rc=$rc err=[$(cat "$TMP/e3")]"
+  fi
+fi
+
+echo "---"
+echo "PASS=$PASS FAIL=$FAIL"
+[ "$FAIL" -eq 0 ]