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/backend/controllers/batch_export_controller.py

@@ -0,0 +1,62 @@
+from __future__ import annotations
+
+import logging
+import threading
+
+from PySide6.QtCore import Property, QObject, Qt, Signal, Slot
+
+from pygui.backend.utils import slot_error_boundary
+from pygui.backend.wafer.batch_export import BatchExportResult, export_batch
+
+log = logging.getLogger(__name__)
+
+
+class BatchExportController(QObject):
+    busyChanged = Signal()
+    exportFinished = Signal(str)
+
+    _batchFinished = Signal(list)
+
+    def __init__(self, parent: QObject | None = None) -> None:
+        super().__init__(parent)
+        self._busy = False
+        self._batchFinished.connect(self._handle_batch_finished, Qt.ConnectionType.QueuedConnection)
+
+    @Property(bool, notify=busyChanged)
+    def busy(self) -> bool:
+        return self._busy
+
+    @Slot("QVariantList", str)
+    def start(self, file_paths: list, output_dir: str) -> None:
+        if self._busy:
+            return
+        self._busy = True
+        self.busyChanged.emit()
+        threading.Thread(
+            target=self._worker, args=(list(file_paths), output_dir), daemon=True
+        ).start()
+
+    def _worker(self, file_paths: list[str], output_dir: str) -> None:
+        try:
+            results = export_batch(file_paths, output_dir)
+        except Exception as exc:
+            log.exception("Batch export worker crashed: %s", exc)
+            results = []
+        self._batchFinished.emit(results)
+
+    @Slot(list)
+    @slot_error_boundary
+    def _handle_batch_finished(self, results: list[BatchExportResult]) -> None:
+        try:
+            total = len(results)
+            succeeded = sum(1 for r in results if r.success)
+            failed = total - succeeded
+            summary = (
+                f"Exported {succeeded}/{total} — {failed} failed"
+                if failed
+                else f"Exported {succeeded}/{total}"
+            )
+            self.exportFinished.emit(summary)
+        finally:
+            self._busy = False
+            self.busyChanged.emit()