Add FAQ about miri test failures

[SF-Zhou]

Added FAQ section explaining the expected failure of miri tests due to Stacked Borrows violation and provided details on the safety of the implementation.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (b2169a9) to head (0d9352a).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #21   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            3         3           
  Lines          870       870           
=========================================
  Hits           870       870           

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[Copilot]

Pull request overview

This PR adds a FAQ section to the README explaining why miri tests fail for this crate. The documentation clarifies that the Stacked Borrows violation is expected and intentional due to the crate's use of raw pointers with moved Box values, and provides justification for why this pattern is safe in practice.

• Added FAQ section with explanation of miri test failures
• Included code example demonstrating the pattern causing the violation
• Provided safety rationale and reference to detailed issue discussion

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