Fix DataArray validation for upstream compatibility

- Skip coord validation for DataArray inputs in arithmetic contexts
  (allow_extra_dims=True) to preserve xarray's native alignment
- Add allow_extra_dims=True to comparison operator and quadratic dot
  as_dataarray calls for consistent broadcasting
- Handle MultiIndex levels in expand_dims guard

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: FBumann

linopy/common.py

@@ -172,6 +172,9 @@ def _validate_dataarray_coords(
     expand = {}
     for k, v in expected.items():
         if k not in arr.dims:
+            # Skip coords that already exist (e.g. MultiIndex levels)
+            if k in arr.coords:
+                continue
             expand[k] = v
             continue
         actual = arr.coords[k]
@@ -240,7 +243,6 @@ def pandas_to_dataarray(
                 " for alignment."
             )
 
-
     return DataArray(arr, coords=None, dims=dims, **kwargs)
 
 
@@ -341,7 +343,7 @@ def as_dataarray(
     elif isinstance(arr, int | float | str | bool | list):
         arr = DataArray(arr, coords=coords, dims=dims, **kwargs)
     elif isinstance(arr, DataArray):
-        if coords is not None:
+        if coords is not None and not allow_extra_dims:
             arr = _validate_dataarray_coords(arr, coords, dims, allow_extra_dims)
     elif not isinstance(arr, DataArray):
         supported_types = [

linopy/expressions.py

@@ -1146,7 +1146,9 @@ def to_constraint(
             )
 
         if isinstance(rhs, SUPPORTED_CONSTANT_TYPES):
-            rhs = as_dataarray(rhs, coords=self.coords, dims=self.coord_dims)
+            rhs = as_dataarray(
+                rhs, coords=self.coords, dims=self.coord_dims, allow_extra_dims=True
+            )
 
             extra_dims = set(rhs.dims) - set(self.coord_dims)
             if extra_dims:
@@ -2197,7 +2199,9 @@ def __matmul__(
                 "Higher order non-linear expressions are not yet supported."
             )
 
-        other = as_dataarray(other, coords=self.coords, dims=self.coord_dims)
+        other = as_dataarray(
+            other, coords=self.coords, dims=self.coord_dims, allow_extra_dims=True
+        )
         common_dims = list(set(self.coord_dims).intersection(other.dims))
         return (self * other).sum(dim=common_dims)