Add unittests for df_utils

[abdulfatir]

Issue #, if available:

Description of changes: This PR improves test coverage by adding unit tests for df_utils. Previously these methods were only being tested as part of Chronos-2 integration tests.

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[Copilot]

Pull request overview

This PR enhances test coverage by adding comprehensive unit tests for the df_utils module, which previously was only tested through Chronos-2 integration tests. The tests thoroughly validate data frame validation and conversion functionality with various scenarios including different frequencies, data types, covariates, and error conditions.

Key Changes

• Added 13 unit tests covering validate_df_inputs and convert_df_input_to_list_of_dicts_input functions
• Tests validate correct behavior with single/multiple targets, past/future covariates, various frequencies, and error handling
• Updated .gitignore to exclude Kiro IDE configuration files

Reviewed changes

Copilot reviewed 1 out of 2 changed files in this pull request and generated no comments.

File	Description
test/test_df_utils.py	Comprehensive unit test suite for df_utils module with 13 test cases covering validation, conversion, dtype casting, error handling, and edge cases
.gitignore	Added .kiro directory exclusion for Kiro IDE configuration files

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[shchur]

LGTM!

[shchur]

🚀