docs: Update resolution docstrings to reference truncate instead of round

[haydena7]

Summary

In dataframely/columns/datetime.py, the docstrings for the Date, Time, Datetime, and Duration classes state that the resolution argument uses the formatting language of the polars datetime round method.

This is semantically confusing, as the actual underlying implementation uses the polars datetime truncate method.

Motivation

While both methods share the same formatting strings, their behavior is materially different. The round method maps values in the second half of an interval to the end of their bucket, whereas truncate maps each value to the start of its bucket. Updating the docstring to reference truncate accurately reflects the strict boundary validation happening under the hood.

Changes

Updated docstrings in Date, Time, Datetime, and Duration to replace "round method" with "truncate method".

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (573b564) to head (769acb7).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

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  Coverage   100.00%   100.00%           
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  Files           54        54           
  Lines         3125      3125           
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  Hits          3125      3125           

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[Copilot]

Pull request overview

This pull request corrects a semantic inaccuracy in the docstrings for datetime-related column types. The docstrings previously referenced the polars round method for the resolution parameter's formatting language, but the actual implementation uses the polars truncate method. While both methods share the same formatting strings, their behavior differs materially: round maps values to bucket endpoints, whereas truncate maps to bucket starts. This documentation update ensures accuracy and clarity for users understanding the strict boundary validation behavior.

Changes:

• Updated docstrings in Date, Time, Datetime, and Duration classes to reference truncate method instead of round method

[borchero]

Thanks!