perf: replace set membership checks with chained == in GAP parser

[bdraco]

Summary

• Replace 3 gap_type_num in {A, B} set-literal membership checks with chained == comparisons in _uncached_parse_advertisement_bytes
• In Cython-compiled code, x in {A, B} creates a frozenset lookup that benchmarks ~2.4x slower than x == A or x == B (0.051 us vs 0.021 us per check)
• These checks fire on every GAP record in the parse loop, so the improvement compounds with advertisement volume

Test plan

• Existing tests pass (no behavioral change, pure refactor)
• Verify Cython compilation succeeds

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (7a74ee9) to head (f5865f1).

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #203   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files            6         6           
  Lines          255       255           
  Branches        38        38           
=========================================
  Hits           255       255           

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[codspeed-hq]

Merging this PR will not alter performance

✅ 9 untouched benchmarks

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_{Comparing optimize-set-membership-to-chained-eq (f5865f1) with main (7a74ee9)}