feat(auditserver): expose MatchFrame library API

[ncode]

This pull request introduces a new library-mode API for evaluating audit log frames outside the event loop, and refactors the rule-group matching logic for improved testability and clarity. The main change is the addition of the MatchFrame method to AuditServer, which allows direct evaluation of raw audit log frames and returns detailed match results. The pull request also adds comprehensive documentation and tests for the new API.

New library-mode API and documentation:

• Added the MatchFrame method to AuditServer, enabling callers to evaluate raw audit log frames and receive a structured MatchResult containing whether any rule group matched, the parsed log, and the names of matched groups.
• Introduced a new package-level documentation in pkg/auditserver/doc.go, describing the library-mode usage and providing example code for MatchFrame.

Refactoring and test coverage:

• Refactored internal frame matching logic by extracting rule-group evaluation into a reusable matchFrame function, simplifying the event loop handling and improving separation of concerns. [1] [2]
• Added extensive unit tests for MatchFrame, covering matching, non-matching, error cases, multiple rule groups, and order preservation, as well as a usage example.
• Introduced a new benchmark for MatchFrame to measure allocation and performance.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.22%. Comparing base (b2bcdbc) to head (8eb5dc0).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #28      +/-   ##
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+ Coverage   96.07%   96.22%   +0.15%     
==========================================
  Files          10       10              
  Lines         611      636      +25     
==========================================
+ Hits          587      612      +25     
  Misses         19       19              
  Partials        5        5              

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