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.

src/pygui/backend/visualization/chart_geometry.py

@@ -31,3 +31,22 @@ def index_to_pixel(index: float, count: int, pixel_start: float, pixel_span: flo
         return pixel_start + pixel_span / 2
     fraction = index / (count - 1)
     return pixel_start + fraction * pixel_span
+
+
+def elapsed_to_pixel(
+    elapsed: float,
+    window_start: float,
+    window_end: float,
+    pixel_start: float,
+    pixel_span: float,
+) -> float:
+    """Map an elapsed-seconds value onto a pixel range, left to right.
+
+    Unlike `value_to_pixel`, this is not inverted: larger elapsed values sit
+    at larger pixel x-coordinates, matching how time flows left-to-right.
+    """
+    window_span = window_end - window_start
+    if window_span < 1e-9:
+        return pixel_start + pixel_span
+    fraction = (elapsed - window_start) / window_span
+    return pixel_start + fraction * pixel_span