improvement: migrate mo.ui.dataframe to narwhals; support duckdb, ibis, pandas, polars

[mscolnick]

This migrates mo.ui.dataframe logic to be backed by narwhals to both 1) reduce maintenance burden, 2) support more dataframe types.

We now support: duckdb, ibis, pandas, polars

This will also fix duckdb filtering when using mo.ui.table()

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Project	Deployment	Preview	Comments	Updated (UTC)
marimo-docs	Ready	Preview	Comment	Oct 14, 2025 7:50pm

[Copilot]

Pull Request Overview

This PR migrates the mo.ui.dataframe component to use narwhals as the backend abstraction layer, expanding support from just pandas and polars to include duckdb, ibis, pandas, and polars. This reduces maintenance burden by consolidating dataframe handling logic under a single API while fixing duckdb filtering when using mo.ui.table().

• Replaces individual transform handlers (PandasTransformHandler, PolarsTransformHandler, IbisTransformHandler) with a unified NarwhalsTransformHandler
• Updates test infrastructure to use parameterized tests with create_dataframes helper
• Changes column ID types from Union[str, int] to str for consistency across backends

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
tests/_plugins/ui/_impl/dataframes/test_print_code.py	Updates tests to use NarwhalsTransformHandler and narwhals lazy dataframes
tests/_plugins/ui/_impl/dataframes/test_handlers.py	Refactors tests to use unified narwhals approach with helper functions
tests/_plugins/ui/_impl/dataframes/test_dataframe.py	Updates dataframe tests to work with narwhals-backed implementation
marimo/_smoke_tests/dataframes/transforms.py	Adds smoke test script for testing transforms across multiple dataframe backends
marimo/_plugins/ui/_impl/dataframes/transforms/types.py	Updates type definitions to use narwhals types and removes int from ColumnId
marimo/_plugins/ui/_impl/dataframes/transforms/handlers.py	Replaces backend-specific handlers with unified NarwhalsTransformHandler
marimo/_plugins/ui/_impl/dataframes/transforms/apply.py	Updates transform application to work with narwhals lazy frames
marimo/_plugins/ui/_impl/dataframes/dataframe.py	Modifies dataframe component to use narwhals internally while preserving external API

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