feat(export): batch wafer-map PNG export from file list

- BatchExport worker + BatchExportController (threaded, busy flag)
- SourcePanel: Export Maps button → FolderDialog → batch export
  with progress/summary banner (dismissible)
- StreamControlPanel: name single export after loaded CSV + timestamp

src/pygui/ISC/Tabs/components/StreamControlPanel.qml

@@ -280,8 +280,16 @@ Rectangle {
                 opacity: enabled ? 1 : 0.4
 
                 onClicked: {
-                    // Default into <saveDataDir>/Export (created on demand)
-                    exportDialog.selectedFile = "file://" + deviceController.exportDir() + "/wafer_map.png"
+                    // Default into <saveDataDir>/Export (created on demand),
+                    // named after the loaded CSV so exports are traceable
+                    // back to their source (falls back to a generic name for
+                    // a live stream with no review file loaded).
+                    var loaded = streamController.loadedFile
+                    var baseName = loaded
+                        ? loaded.split("/").pop().replace(/\.[^.]+$/, "")
+                        : "wafer_map"
+                    var ts = Qt.formatDateTime(new Date(), "yyyyMMdd_HHmmss")
+                    exportDialog.selectedFile = "file://" + deviceController.exportDir() + "/" + baseName + "_" + ts + ".png"
                     exportDialog.open()
                 }