Row-wise Mode Functionality (Dask Issue #11389)

[thyripian]

I conducted a brief search to confirm if this has already been opened here.

Dask Issue #11389 requested the addition of row-wise mode functionality for DataFrames. Through extensive research and testing, I found that the necessary modifications had to be made within dask_expr/_collection.py in the dask-expr repository.

I’m submitting this issue to formally document the need for these changes, and I plan to submit a PR shortly to support this. The code changes are already complete and have been thoroughly tested locally—PR submitted, pending approval.