Add runnable examples to CTable where and sort_by

[armutlutost]

Summary

Add runnable examples to the CTable.where() and CTable.sort_by() docstrings.

The examples demonstrate filtering, column projection, compound predicates, plain sorting, lazy sorting of a filtered view, and multi-key sorting.

Closes #650

Changes

• Add a complete sample CTable setup to both docstrings.
• Demonstrate where() with a simple predicate and selected columns.
• Demonstrate a compound column predicate.
• Demonstrate materialized and lazy sorting.
• Add a multi-key sorting example.
• Include printed results that clarify lazy view behavior.

Validation

• python -m py_compile src/blosc2/ctable.py
• git diff --check

The repository’s required blosc2 Conda environment was unavailable locally, so the documentation examples were not executed against the compiled extension.

AI disclosure

AI assistance was used to draft the documentation examples. I reviewed the changes before submitting this pull request.