Add MCP bridge for external tool integration

Embedded JSON-RPC server over named pipes (rcx-mcp) enabling external
tools like Claude Code to inspect and manipulate the node tree, read/write
hex data, switch sources, and trigger UI actions. Includes stdio adapter
(rcx-mcp-stdio) for stdin/stdout transport. Server is stopped by default;
user starts via File > Start MCP Server.

Also extracts MainWindow class declaration to mainwindow.h and improves
type selector popup Esc button styling.

src/mainwindow.h

@@ -0,0 +1,119 @@
+#pragma once
+#include "controller.h"
+#include "pluginmanager.h"
+#include <QMainWindow>
+#include <QMdiArea>
+#include <QMdiSubWindow>
+#include <QLabel>
+#include <QSplitter>
+#include <QTabWidget>
+#include <QDockWidget>
+#include <QTreeView>
+#include <QStandardItemModel>
+#include <QMap>
+#include <Qsci/qsciscintilla.h>
+
+namespace rcx {
+
+class McpBridge;
+
+class MainWindow : public QMainWindow {
+    Q_OBJECT
+    friend class McpBridge;
+public:
+    explicit MainWindow(QWidget* parent = nullptr);
+
+private slots:
+    void newFile();
+    void newDocument();
+    void selfTest();
+    void openFile();
+    void saveFile();
+    void saveFileAs();
+
+
+    void addNode();
+    void removeNode();
+    void changeNodeType();
+    void renameNodeAction();
+    void duplicateNodeAction();
+    void splitView();
+    void unsplitView();
+
+    void undo();
+    void redo();
+    void about();
+    void toggleMcp();
+    void setEditorFont(const QString& fontName);
+    void exportCpp();
+    void showTypeAliasesDialog();
+    void editTheme();
+
+public:
+    // Project Lifecycle API
+    QMdiSubWindow* project_new();
+    QMdiSubWindow* project_open(const QString& path = {});
+    bool project_save(QMdiSubWindow* sub = nullptr, bool saveAs = false);
+    void project_close(QMdiSubWindow* sub = nullptr);
+
+private:
+    enum ViewMode { VM_Reclass, VM_Rendered };
+
+    QMdiArea* m_mdiArea;
+    QLabel*   m_statusLabel;
+    PluginManager m_pluginManager;
+    McpBridge*    m_mcp       = nullptr;
+    QAction*      m_mcpAction = nullptr;
+
+    struct SplitPane {
+        QTabWidget*    tabWidget = nullptr;
+        RcxEditor*     editor    = nullptr;
+        QsciScintilla* rendered  = nullptr;
+        ViewMode       viewMode  = VM_Reclass;
+        uint64_t       lastRenderedRootId = 0;
+    };
+
+    struct TabState {
+        RcxDocument*       doc;
+        RcxController*     ctrl;
+        QSplitter*         splitter;
+        QVector<SplitPane> panes;
+        int                activePaneIdx = 0;
+    };
+    QMap<QMdiSubWindow*, TabState> m_tabs;
+
+
+    void createMenus();
+    void createStatusBar();
+    void showPluginsDialog();
+    QIcon makeIcon(const QString& svgPath);
+
+    RcxController* activeController() const;
+    TabState* activeTab();
+    TabState* tabByIndex(int index);
+    int tabCount() const { return m_tabs.size(); }
+    QMdiSubWindow* createTab(RcxDocument* doc);
+    void updateWindowTitle();
+
+    void setViewMode(ViewMode mode);
+    void updateRenderedView(TabState& tab, SplitPane& pane);
+    void updateAllRenderedPanes(TabState& tab);
+    uint64_t findRootStructForNode(const NodeTree& tree, uint64_t nodeId) const;
+    void setupRenderedSci(QsciScintilla* sci);
+
+    SplitPane createSplitPane(TabState& tab);
+    void applyTheme(const Theme& theme);
+    void applyTabWidgetStyle(QTabWidget* tw);
+    SplitPane* findPaneByTabWidget(QTabWidget* tw);
+    SplitPane* findActiveSplitPane();
+    RcxEditor* activePaneEditor();
+
+    // Workspace dock
+    QDockWidget*        m_workspaceDock  = nullptr;
+    QTreeView*          m_workspaceTree  = nullptr;
+    QStandardItemModel* m_workspaceModel = nullptr;
+    void createWorkspaceDock();
+    void rebuildWorkspaceModel();
+};
+
+} // namespace rcx