Implemented qt port + e2e

Client/streamhub-qt/SourceSidebar.h

@@ -0,0 +1,44 @@
+/**
+ * @file SourceSidebar.h
+ * @brief Source browser sidebar: tree of sources → signals with drag-to-plot.
+ *
+ * Mirrors the ImGui SourcePanel. Each signal leaf is draggable; the drag
+ * payload is the mime type "application/x-shq-signal" carrying two qint32
+ * values {sourceIdx, signalIdx}, consumed by PlotWidget's drop handler.
+ */
+
+#pragma once
+
+#include <QWidget>
+
+class QTreeWidget;
+class QTreeWidgetItem;
+
+namespace shq {
+
+class Hub;
+
+/** MIME type carried by a signal drag: payload = qint32[2] {srcIdx,sigIdx}. */
+extern const char* const kMimeSignal;
+
+class SourceSidebar : public QWidget {
+    Q_OBJECT
+public:
+    explicit SourceSidebar(Hub* hub, QWidget* parent = nullptr);
+
+public Q_SLOTS:
+    /** Rebuild the tree from the current model (sources/config changes). */
+    void refresh();
+
+Q_SIGNALS:
+    /** User clicked "Add Source" (MainWindow opens the dialog). */
+    void addSourceRequested();
+
+private:
+    void onContextMenu(const QPoint& pos);
+
+    Hub*         hub_;
+    QTreeWidget* tree_ = nullptr;
+};
+
+} /* namespace shq */