Hardcode chat memory to 4 turns (lock history_turns slider)

The history_turns control is now non-interactive and fixed at
MAX_HISTORY_TURNS (4). It stays in additional_inputs so the /respond
API signature is unchanged (message, top_k, self_correct, history_turns).

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

app.py

@@ -72,9 +72,12 @@ with gr.Blocks(title="GDScript Coding Assistant", fill_height=True) as demo:
         top_k = gr.Slider(2, 10, value=6, step=1, label="Retrieved snippets (k)")
         self_correct = gr.Checkbox(
             value=True, label="Auto-correct one syntax error (extra GPU call)")
+        # Chat memory is hardcoded to 4 turns. Kept as a non-interactive input
+        # (rather than removed) so the /respond API signature stays
+        # (message, top_k, self_correct, history_turns).
         history_turns = gr.Slider(
-            0, 8, value=promptlib.MAX_HISTORY_TURNS, step=1,
-            label="Chat memory: prior turns to remember (0 = single-turn)")
+            0, 8, value=promptlib.MAX_HISTORY_TURNS, step=1, interactive=False,
+            label=f"Chat memory: fixed at {promptlib.MAX_HISTORY_TURNS} prior turns")
 
     gr.ChatInterface(
         fn=respond,