docs(dataframe): improve dataframe! and from_columns documentation (#…

[cj-zhukov]

…24430)

Which issue does this PR close?

• Closes #docs(dataframe): improve dataframe! and from_columns documentation #24430.

Rationale for this change

This is a follow-up to #16090 to improve the documentation of thedataframe! macro and DataFrame::from_columns() API.

What changes are included in this PR?

• Align the documentation examples with the existing patterns in the dataframe module.
• Update the public API descriptions to better match the codebase conventions.
• Add executable examples that verify the expected DataFrame output.

These changes make the APIs easier for users to discover and understand.

Are these changes tested?

Yes. The updated documentation examples are tested.

Are there any user-facing changes?

Yes. This PR improves the documentation and examples for dataframe! and DataFrame::from_columns().

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.23%. Comparing base (bb038a6) to head (dfdb728).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #24434      +/-   ##
==========================================
- Coverage   81.23%   81.23%   -0.01%     
==========================================
  Files        1112     1112              
  Lines      390635   390635              
  Branches   390635   390635              
==========================================
- Hits       317350   317338      -12     
- Misses      54650    54656       +6     
- Partials    18635    18641       +6     

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