Remove unused Mutability enum and small docs/cleanup

[Code0x58]

Motivation

• Remove an unused enum and its import to simplify the codebase and avoid dead code.
• Fix README formatting so the file ends with a newline and clarify the examples reference.

Testing

• Ran the project test suite with pytest and the tests completed successfully.
• Ran the codebase checks (basic import and lint passes) to ensure no import or syntax regression.

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Codex Task

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (1f7f06d) to head (71f3581).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff            @@
##            master       #10   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         1           
  Lines          202       194    -8     
=========================================
- Hits           202       194    -8     

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