feat(ui): add minibuffer history

Implemented input history for the minibuffer, navigable via Up/Down arrows. History persists across mode switches during the session.

src/gtk_editor.cpp

@@ -154,6 +154,8 @@ private:
     Mode mode_ = Mode::Normal;
     std::string command_buffer_;
     std::string message_line_;
+    std::vector<std::string> minibuffer_history_;
+    size_t history_index_ = 0;
 
     // Member variables
     Gtk::DrawingArea* drawing_area_ = nullptr; // For single-window compatibility
@@ -945,6 +947,12 @@ protected:
             }
             
             if (key_name == "Return") {
+                // Add to history
+                if (!command_buffer_.empty() && (minibuffer_history_.empty() || minibuffer_history_.back() != command_buffer_)) {
+                    minibuffer_history_.push_back(command_buffer_);
+                }
+                history_index_ = minibuffer_history_.size();
+
                 // Execute command logic
                 if (mode_ == Mode::Command) {
                     if (command_buffer_ == "quit" || command_buffer_ == "q") {
@@ -970,6 +978,29 @@ protected:
                 return true;
             }
             
+            // History Navigation
+            if (key_name == "ArrowUp") {
+                if (history_index_ > 0) {
+                    history_index_--;
+                    command_buffer_ = minibuffer_history_[history_index_];
+                    if (content_widget_) queue_redraw_all_windows(content_widget_);
+                }
+                return true;
+            }
+
+            if (key_name == "ArrowDown") {
+                if (history_index_ < minibuffer_history_.size()) {
+                    history_index_++;
+                    if (history_index_ == minibuffer_history_.size()) {
+                         command_buffer_.clear(); 
+                    } else {
+                         command_buffer_ = minibuffer_history_[history_index_];
+                    }
+                    if (content_widget_) queue_redraw_all_windows(content_widget_);
+                }
+                return true;
+            }
+            
             if (key_name == "Backspace") {
                 if (!command_buffer_.empty()) command_buffer_.pop_back();
                 if (content_widget_) queue_redraw_all_windows(content_widget_);