feat(map): add edge-center delta stats, thickness overlay, and layout fix

- Add edge-center sensor pair tables and delta calculations per wafer family.
- Parse and interpolate wafer thickness CSV data for offscreen visualization.
- Refactor ReadoutPanel layout using Item + anchors to fix right-margin clipping.
- Compact E-C Delta text format to fit standard sidebar width.
- Add pytest suite covering delta calculations, layout pairs, and thickness CSV.

src/pygui/backend/models/sensor_editor.py

@@ -28,6 +28,11 @@ class SensorEditor:
     def has_overrides(self) -> bool:
         return bool(self._replacements or self._offsets)
 
+    def replaced_indices(self) -> set[int]:
+        """Sensors whose value is a replacement (offsets don't count — an
+        offset sensor still reads from its physical location)."""
+        return set(self._replacements)
+
     def active_indices(self) -> list[int]:
         """Return sorted sensor indices that have any override."""
         return sorted(set(self._replacements) | set(self._offsets))