Remove UnivariateDriftCalculator from codebase

[Copilot]

This PR removes the UnivariateDriftCalculator class from the codebase as it was only used internally and provides overlapping functionality with the existing DriftCalculator class.

Changes Made

• Removed UnivariateDriftCalculator class from tab_right/drift/univariate.py (122 lines)
• Refactored detect_univariate_drift_df() to implement the logic directly instead of using the class
• Removed 6 test functions that specifically tested UnivariateDriftCalculator (69 lines)
• Cleaned up imports by removing unused dataclass and Union imports

Benefits

• Cleaner codebase: Eliminates redundant drift detection implementation
• Reduced maintenance burden: One less class to maintain and document
• Preserved public API: All existing functions (detect_univariate_drift, detect_univariate_drift_df, etc.) work identically
• No breaking changes: Documentation examples and notebooks continue to work without modification

Verification

• ✅ All 130 tests pass
• ✅ Code passes linting checks
• ✅ Public API behavior preserved for all scenarios:

  # These continue to work exactly as before
  detect_univariate_drift_df(df1, df2)  # auto detection
  detect_univariate_drift_df(df1, df2, kind="continuous")  # forced type
  detect_univariate_drift(series1, series2)  # individual series

The DriftCalculator class remains available for users who need object-oriented drift analysis, while the functional APIs provide a simpler interface for most use cases.

Fixes #112.

[codecov]

Codecov Report

Attention: Patch coverage is 88.88889% with 2 lines in your changes missing coverage. Please review.

Project coverage is 95.76%. Comparing base (d5203cc) to head (9c3bd3e).

Files with missing lines	Patch %	Lines
tab_right/drift/univariate.py	88.88%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #113      +/-   ##
==========================================
- Coverage   95.78%   95.76%   -0.03%     
==========================================
  Files          19       19              
  Lines         736      708      -28     
==========================================
- Hits          705      678      -27     
+ Misses         31       30       -1     

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