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

tests/test_batch_export_controller.py

@@ -0,0 +1,59 @@
+"""Tests for src/pygui/backend/controllers/batch_export_controller.py."""
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from pygui.backend.controllers.batch_export_controller import BatchExportController
+from pygui.backend.wafer.batch_export import BatchExportResult
+
+pytestmark = pytest.mark.usefixtures("qapp")
+
+
+@pytest.fixture
+def controller():
+    return BatchExportController()
+
+
+def test_start_spawns_thread_and_sets_busy(controller):
+    with patch("threading.Thread") as mock_thread:
+        controller.start(["a.csv", "b.csv"], "/tmp/out")
+        mock_thread.assert_called_once()
+        assert controller.busy is True
+
+
+def test_start_ignores_call_while_already_busy(controller):
+    with patch("threading.Thread") as mock_thread:
+        controller.start(["a.csv"], "/tmp/out")
+        controller.start(["b.csv"], "/tmp/out")
+        mock_thread.assert_called_once()
+
+
+def test_handle_batch_finished_reports_all_succeeded(controller):
+    finished = MagicMock()
+    controller.exportFinished.connect(finished)
+    controller._busy = True
+
+    results = [
+        BatchExportResult("a.csv", "a.png", True),
+        BatchExportResult("b.csv", "b.png", True),
+        BatchExportResult("c.csv", "c.png", True),
+    ]
+    controller._handle_batch_finished(results)
+
+    finished.assert_called_once_with("Exported 3/3")
+    assert controller.busy is False
+
+
+def test_handle_batch_finished_reports_failures(controller):
+    finished = MagicMock()
+    controller.exportFinished.connect(finished)
+    controller._busy = True
+
+    results = [
+        BatchExportResult("a.csv", "a.png", True),
+        BatchExportResult("b.csv", "b.png", False, "parse error"),
+    ]
+    controller._handle_batch_finished(results)
+
+    finished.assert_called_once_with("Exported 1/2 — 1 failed")
+    assert controller.busy is False