This pull request introduces significant improvements to the security of the Polars code execution sandbox, enhances documentation clarity, and adds comprehensive tests for the new security features. The most important changes are summarized below.

Security hardening for Polars code execution:

• The PolarsCodeParser now enforces a strict set of blocked functions (e.g., open, exec, eval, __import__, etc.), blocks all import statements, and restricts access to dunder (double underscore) attributes and strings, preventing common sandbox escape vectors. Additionally, the execution environment's __builtins__ is set to an empty dictionary to block access to all built-in functions unless explicitly allowed. [1] [2]

Expanded security test coverage:

• A new TestPolarsCodeParserSecurity class is added with extensive tests covering blocked function calls, import statements, dunder access, bypass attempts, and runtime enforcement to ensure the sandbox is robust against known and potential attacks. The tests also verify that allowed operations and Polars functionality continue to work as expected.

Documentation improvements:

• The user documentation for the catalog and kernel features has been updated for clarity and accuracy. This includes removing references to Unity Catalog, simplifying sidebar tab descriptions, clarifying artifact persistence (removing outdated recovery mode details), and updating I/O function descriptions. Unnecessary or outdated sections on execution cancellation and resource monitoring have been removed for conciseness. [1] [2] [3] [4] [5] [6]

Other code and test maintenance:

• Minor import adjustments to support the new test structure and maintain code clarity.