`generateInitialTensorForPartialReduction` and the `getInitSliceInfo*`
helpers unconditionally cast every result expression of the partial
result AffineMap to `AffineDimExpr`. When the original output indexing
map contains a constant (e.g. `affine_map<(d0,d1,d2)->(d0,0,d2)>`), the
constant expression propagates into the partial map and the cast
triggers an assertion.
Fixes#173025
Assisted-by: Claude Code