gui: category tree, menus, toolbar, splitter — build-order step 3

- CategoryPanel: the left tree — All Downloads / Unfinished / Finished,
  then Categories and Queues populated from category.list / queue.list,
  with per-node task counts. Selecting a node emits a TaskSelection.
- DownloadFilterProxy: QSortFilterProxyModel keyed off that selection.
  Client-side for M1 (the whole list fits); asTaskFilter() exposes the
  equivalent TaskFilter for a server-side download.list once paging lands.
- MainWindow: menu bar (Tasks / Downloads / View / Help) sharing QAction
  objects with the toolbar; QSplitter [panel | table]; Delete with a
  confirm; Resume/Pause All; View menu toggles the panel. Actions
  disabled while offline.
- Counts are computed off a throttled 400 ms timer, not the 4 Hz progress
  path. Fixed a debounce-vs-throttle bug found in the first screenshot:
  restarting the timer on every progress tick meant it never fired and
  the status bar sat at "0 of 0 downloads".
- First-run column widths that fit the content.
- tst_downloadfilterproxy: nodes filter to their own rows, the
  Finished/Unfinished split is correct, and the filter is dynamic (a row
  that finishes leaves the Unfinished node with no re-list). Verified
  against mockd --tasks 400 (screenshot: tree counts 75/84/89/83/69 sum
  to 400, status bar "400 of 400, 21 active").

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_016Ne28kx4VreeBWZv82Nksd

gui/src/mainwindow/MainWindow.hpp

@@ -1,22 +1,26 @@
 // The main window. Lane GUI.
 //
-// M1 slice: category tree, dialogs and the tray come later. This is the table driven by
-// mockd, a status-bar connection dot, an offline banner instead of a modal, and the three
-// selection actions that need no dialog (pause / resume / cancel).
+// M1 slice: dialogs and the tray still come later. This is the menus + toolbar + splitter
+// (category tree | table), the table driven by mockd, a status-bar connection dot, an
+// offline banner instead of a modal, and the actions that need no dialog.
 
 #pragma once
 
+#include <QHash>
 #include <QMainWindow>
 
+#include "models/DownloadFilterProxy.hpp"
 #include "rpc/Protocol.hpp"
 
+class QAction;
 class QLabel;
-class QSortFilterProxyModel;
+class QTimer;
 class QTreeView;
 
 namespace velox::gui {
 
 class DownloadTableModel;
+class CategoryPanel;
 namespace rpc {
 class RpcClient;
 }  // namespace rpc
@@ -34,27 +38,47 @@ class MainWindow : public QMainWindow {
   private slots:
     void onConnectionState(rpc::ConnectionState state);
     void onSpeedGlobal(const QJsonObject &params);
-    void updateCounts();
+    void onFilterChanged(const velox::gui::TaskSelection &selection);
+    void scheduleCounts();  // throttled: fires refreshCounts() at most every 400 ms
+    void refreshCounts();
 
     void pauseSelection();
     void resumeSelection();
     void cancelSelection();
+    void removeSelection();
+    void resumeAll();
+    void pauseAll();
 
   private:
+    void buildActions();
+    void buildMenus();
+    void buildToolBar();
+    void fetchTree();
     QStringList selectedTaskIds() const;
-    void actOnSelection(const char *methodName);
+    QStringList allTaskIds() const;
+    void actOnTasks(const char *methodName, const QStringList &ids);
     void restoreLayout();
     void saveLayout();
 
     rpc::RpcClient *client_;
     DownloadTableModel *model_;
-    QSortFilterProxyModel *proxy_;
+    DownloadFilterProxy *proxy_;
     QTreeView *view_;
+    CategoryPanel *panel_;
+
+    QAction *actAddUrl_ = nullptr;
+    QAction *actResume_ = nullptr;
+    QAction *actPause_ = nullptr;
+    QAction *actStop_ = nullptr;
+    QAction *actRemove_ = nullptr;
+    QAction *actResumeAll_ = nullptr;
+    QAction *actPauseAll_ = nullptr;
 
     QLabel *connDot_;
     QLabel *connText_;
     QLabel *countsLabel_;
     QWidget *offlineBanner_;
+    QTimer *countsTimer_;
 
     qint64 globalDownBps_ = 0;
 };