Add NDJSON support in polars

[AvinashYerra]

This PR implements NDJSON (newline-delimited JSON) reader and writer support for Polars, following the same pattern as the existing JSON reader/writer implementation.
coming from #1197

Changes

• Added PolarsNDJSONReader class in hamilton/plugins/polars_post_1_0_0_extensions.py

• Added PolarsNDJSONWriter class in hamilton/plugins/polars_post_1_0_0_extensions.py

• Supports writing NDJSON files using data.write_ndjson()

• Registered both classes in register_data_loaders() function to make them available through the materialization system

• Added the following tests:

  • test_polars_ndjson() in tests/plugins/test_polars_extensions.py for DataFrame support
  • test_polars_ndjson() in tests/plugins/test_polars_lazyframe_extensions.py for LazyFrame support

• Added example in examples/polars/materialization/my_script.py

How I tested this

Ran the specific NDJSON tests:

• pytest tests/plugins/test_polars_extensions.py::test_polars_ndjson -v
• pytest tests/plugins/test_polars_lazyframe_extensions.py::test_polars_ndjson -v
  Both tests passed

Notes

Checklist

• [Y] PR has an informative and human-readable title (this will be pulled into the release notes)
• Changes are limited to a single goal (no scope creep)
• [Y] Code passed the pre-commit check & code is left cleaner/nicer than when first encountered.
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged / future TODOs are captured in comments
• Project documentation has been updated if adding/changing functionality.

[skrawcz]

@AvinashYerra would you mind rebasing against the latest hamilton main? I should have merged a fix for a bunch of unit tests.

[AvinashYerra]

Done @skrawcz, rebased to latest main. Thanks!

[skrawcz]

ugh sorry -- fix here #1437 -- if you wanted to apply it to this PR that would also work...

[skrawcz]

One more rebase please :)

[AvinashYerra]

Hi @skrawcz , just for confirmation. you want me to rebase to the latest main right?

[AvinashYerra]

Hi @skrawcz , just for confirmation. you want me to rebase to the latest main right?

it is saying everything is up to date

[skrawcz]

Strange. You can see that I merged #1437 ? So it's on main. Do you have that commit?

[AvinashYerra]

@skrawcz, It is done now.

[AvinashYerra]

Hi @skrawcz , hope you had a great weekend. Can you check now whether the PR is mergeable

[skrawcz]

thanks!