Add tests for mismatch/mismatch_apertures promoting dispatch (90.5% → 93.8%)

[kdw503]

Summary

• Adds a new testset covering the previously-untested protocol entry points:
  • mismatch(non-AbstractFloat arrays, …) → promotes to Float32 (line 80)
  • mismatch_apertures(AbstractFloat arrays, …) → typed dispatch (line 82)
  • mismatch_apertures(non-AbstractFloat arrays, …) → promotes to Float32 (line 83)
  • mismatch_apertures(::Type{T}, fixed, moving, gridsize, maxshift) → gridsize form (lines 85–89)
• Uses the same local-stub pattern already established in the register_translate testset
• Coverage: 90.5% → 93.8%

Remaining uncovered region

Lines 610–635: extraunsafe_view, _tail, get_index_wo_boundcheck, unsafe_reindex — internal unsafe-view helpers only exercised by downstream FFT implementations (RegisterMismatch, RegisterMismatchCuda). An existing # TODO: redesign comment marks them for future attention.

Test plan

• 327/327 tests passing

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.80%. Comparing base (6e8629b) to head (ec85d24).

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #24      +/-   ##
==========================================
+ Coverage   90.49%   93.80%   +3.30%     
==========================================
  Files           1        1              
  Lines         242      242              
==========================================
+ Hits          219      227       +8     
+ Misses         23       15       -8     

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