feat(map): add batch export and adjust layout alignment

- Implement synchronous offscreen wafer map PNG rendering and CSV summary.
- Add "Batch Export" button to file browser sidebar.
- Adjust trend pane bottom spacer to align with About button when visible.
- Fix type check errors and add pytest coverage for batch export.

tests/test_chart_geometry.py

@@ -1,6 +1,10 @@
 import pytest
 
-from pygui.backend.visualization.chart_geometry import index_to_pixel, value_to_pixel
+from pygui.backend.visualization.chart_geometry import (
+    elapsed_to_pixel,
+    index_to_pixel,
+    value_to_pixel,
+)
 
 
 def test_value_to_pixel_min_maps_to_bottom():
@@ -26,3 +30,23 @@ def test_index_to_pixel_first_and_last():
 
 def test_index_to_pixel_single_point_centers():
     assert index_to_pixel(0, 1, pixel_start=0.0, pixel_span=100.0) == pytest.approx(50.0)
+
+
+def test_elapsed_to_pixel_window_start_maps_to_left():
+    assert elapsed_to_pixel(10.0, window_start=10.0, window_end=70.0,
+                             pixel_start=0.0, pixel_span=200.0) == pytest.approx(0.0)
+
+
+def test_elapsed_to_pixel_window_end_maps_to_right():
+    assert elapsed_to_pixel(70.0, window_start=10.0, window_end=70.0,
+                             pixel_start=0.0, pixel_span=200.0) == pytest.approx(200.0)
+
+
+def test_elapsed_to_pixel_midpoint():
+    assert elapsed_to_pixel(40.0, window_start=10.0, window_end=70.0,
+                             pixel_start=0.0, pixel_span=200.0) == pytest.approx(100.0)
+
+
+def test_elapsed_to_pixel_degenerate_window_pins_right():
+    assert elapsed_to_pixel(5.0, window_start=5.0, window_end=5.0,
+                             pixel_start=0.0, pixel_span=200.0) == pytest.approx(200.0)