Force legacy mode for demo data, restore hidden run_grid, clarify demo label

app.py

@@ -87,6 +87,13 @@ def score(
             raise gr.Error("Upload BOTH training & test CSVs *or* tick the demo-data box.")
         train_path, test_path = train_csv.name, test_csv.name
 
+    # ------------------------------------------------------------------
+    # Legacy-mode override for demo data
+    # ------------------------------------------------------------------
+    if use_demo:
+        run_full_grid = False   # ignore any mischievous client-side tweak
+        model = None            # guarantees legacy path (no --model)
+
     out_file = TMP_DIR / f"scores_{uuid4().hex}.csv"
     import atexit, functools
     atexit.register(functools.partial(out_file.unlink, missing_ok=True))
@@ -143,9 +150,9 @@ with gr.Blocks(title="UCI Phonotactic Calculator") as demo:
             test_in  = gr.File(label="Test CSV")
 
             use_demo = gr.Checkbox(
-                label="Use packaged English demo data (recommended)",
+                label="Use packaged English demo data (16-col legacy mode)",
                 value=True,
-                info="Try the built-in English demo first! Upload your own data to run custom experiments."
+                info="Runs the original 2018 output format. Untick and upload your own data to use any model/grid."
             )
 
             model_dd = gr.Dropdown(
@@ -153,11 +160,11 @@ with gr.Blocks(title="UCI Phonotactic Calculator") as demo:
                 value="ngram",
                 label="Model plug-in"
             )
-            # run_grid = gr.Checkbox(label="Run full variant grid", value=False)  # HIDDEN FOR NOW
+            # Hidden checkbox keeps the variable alive for go_btn.click;
+            # power-users can un-hide it in the inspector if they want.
+            run_grid = gr.Checkbox(visible=False, value=False, label="Run full variant grid")
             n_slider = gr.Slider(1, 4, step=1, value=2, label="n-gram order")
 
-            # Remove run_grid.change(...)
-
             with gr.Accordion("Advanced", open=False):
                 filt_txt = gr.Textbox(
                     label="Filter (space-separated key=value …)",