fix(terrain): preserve opaque shade lookup keys

crates/fparkan-terrain-format/src/lib.rs

@@ -212,18 +212,15 @@ pub struct TerrainMaterialPair {
 }
 
 impl TerrainMaterialPair {
-    /// Returns the material-manager selection used by `GetShade`.
+    /// Returns the opaque lookup key supplied to `GetShade`.
     ///
-    /// `GetShade` owns a manager loaded only with `Shade.wea`, so its
-    /// 16-bit lookup occupies row bits of that manager's table zero. It is
-    /// deliberately separate from the `Land1.wea`/`Land2.wea` selections
-    /// carried by [`TerrainMaterialLayers`].
+    /// This is deliberately separate from the `Land1.wea`/`Land2.wea`
+    /// selectors carried by [`TerrainMaterialLayers`]. Although `GetShade`
+    /// owns a manager loaded from `Shade.wea`, this key is not a WEAR row:
+    /// observed map values exceed that table's row count.
     #[must_use]
-    pub const fn shade_selection(self) -> TerrainMaterialSelection {
-        TerrainMaterialSelection {
-            table_index: 0,
-            material_index: self.material_lookup,
-        }
+    pub const fn shade_lookup_key(self) -> u16 {
+        self.material_lookup
     }
 }
 
@@ -1586,11 +1583,8 @@ mod tests {
             ])
         );
         assert_eq!(
-            document.slot_material_pairs(0).expect("material pairs")[0].shade_selection(),
-            TerrainMaterialSelection {
-                table_index: 0,
-                material_index: 0x0102,
-            }
+            document.slot_material_pairs(0).expect("material pairs")[0].shade_lookup_key(),
+            0x0102
         );
         assert_eq!(document.slot_material_pairs(1), None);