chore: format codebase and harden v3 CLI/CI gates

scripts/tui3_coverage_gate.sh

@@ -0,0 +1,39 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+mkdir -p artifacts/coverage
+
+if [[ -x ".venv/bin/python" ]]; then
+    py_bin=".venv/bin/python"
+elif command -v python >/dev/null 2>&1; then
+    py_bin="python"
+else
+    py_bin="python3"
+fi
+
+if ! "$py_bin" - <<'PY' >/dev/null 2>&1
+import importlib.util
+raise SystemExit(0 if importlib.util.find_spec("textual") else 1)
+PY
+then
+    if [[ "${REQUIRE_TEXTUAL:-0}" == "1" ]]; then
+        echo "Error: textual runtime is unavailable; cannot run TUI v3 coverage gate." >&2
+        exit 1
+    fi
+    echo "tui3 coverage gate: skipped (textual runtime unavailable)"
+    exit 0
+fi
+
+"$py_bin" -m pytest -q \
+    --cov=src \
+    --cov-report=json:artifacts/coverage/coverage.tui3_gate.json \
+    src/tests/test_tui_v3_parity.py \
+    src/tests/test_tui_v3_smoke.py
+
+"$py_bin" scripts/check_critical_coverage.py \
+    artifacts/coverage/coverage.tui3_gate.json \
+    --no-default-thresholds \
+    --threshold src/seedpass/tui_v3/app.py=35 \
+    --json-output artifacts/coverage/critical_gate.tui3.json
+
+echo "tui3 coverage gate: ok"