fix(tui): only show help menu on '?' when input is empty (#494)

Previously, pressing '?' would always open the help menu regardless
of whether there was text in the input field. This made it impossible
to type the '?' character when composing prompts.

Now, pressing '?' will:
- Open the help menu if the input is empty
- Type '?' into the input if there is existing text

This allows French keyboard users and others to type '?' while still
providing quick access to help when the prompt is empty.

Co-authored-by: Droid Agent <droid@factory.ai>

Author: echobt

cortex-tui/src/runner/event_loop.rs

@@ -1952,6 +1952,21 @@ impl EventLoop {
                     return Ok(());
                 }
 
+                // Handle '?' key specially: only show help when input is empty
+                // Otherwise, type '?' into the input
+                if action == KeyAction::Help
+                    && key_event.code == KeyCode::Char('?')
+                    && context == ActionContext::Input
+                    && !self.app_state.input.is_empty()
+                {
+                    // Type '?' into the input instead of opening help
+                    self.app_state.text_selection.clear();
+                    self.app_state.input.handle_key(key_event);
+                    self.update_autocomplete();
+                    self.render(terminal)?;
+                    return Ok(());
+                }
+
                 // Forward key events to input widget when focused and no action mapped
                 // This allows character input, backspace, delete, etc. to work
                 if context == ActionContext::Input && action == KeyAction::None {