test(validation): --gui option to run the suite in the GUI

Adds `--gui` to test/validation/run.sh: drops `-b` so testium opens the GUI
with the validation suite loaded instead of running headless. The run is
started manually and the window stays open — handy to inspect the test
tree, try the Ctrl+F search, etc. Works with any --mode.

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

test/validation/run.sh

@@ -3,11 +3,15 @@
 # testium (source, wheel, pyinstaller, flatpak, appimage).
 #
 # Usage:
-#   ./test/validation/run.sh [clean] [--mode MODE] [extra testium args]
+#   ./test/validation/run.sh [clean] [--mode MODE] [--gui] [extra testium args]
 #
 #   clean           remove the validation venv before recreating it
 #                   (must be the first argument; useful after a Python upgrade)
 #
+#   --gui           open the GUI with the suite loaded instead of running in
+#                   batch; run it manually from the window, which stays open
+#                   (handy to inspect the tree, try the Ctrl+F search, ...)
+#
 #   --mode MODE     which testium build to validate. One of:
 #                       source       (default) src/testium via project run.sh
 #                       wheel        dist/testium-<v>-py3-none-any.whl
@@ -45,6 +49,8 @@ else
 fi
 
 EXTRA=()
+RUN_FLAGS=(-b)            # batch by default; --gui opens the GUI and stays open
+GUI=0
 while [ $# -gt 0 ]; do
     case "$1" in
         --mode)
@@ -55,6 +61,11 @@ while [ $# -gt 0 ]; do
             MODE="${1#--mode=}"
             shift
             ;;
+        --gui)
+            GUI=1
+            RUN_FLAGS=()     # no -b: launch the GUI with the suite loaded,
+            shift            # run it manually; the window does not auto-close
+            ;;
         *)
             EXTRA+=("$1")
             shift
@@ -147,7 +158,11 @@ echo "-- launch: ${CMD[*]}"
 echo "-- LSP check ($MODE)"
 "$VENV_PYTHON" "$SCRIPT_DIR/lsp_check.py" "${CMD[@]}"
 
-exec "${CMD[@]}" -b \
+if [ "$GUI" -eq 1 ]; then
+    echo "-- GUI mode: the suite is loaded; press Start to run. Window stays open."
+fi
+
+exec "${CMD[@]}" "${RUN_FLAGS[@]}" \
     -d "python_bin=$VENV_PYTHON" \
     -d "validation_report_file=validation-$MODE" \
     -- "$SCRIPT_DIR/main.tum" "${EXTRA[@]}"