Ignixa L2: Import performance baseline and compatibility corpus

[Brendan Kowitz (brendankowitz)]

Summary

Implements the L2 stacked PR on top of #5801 (feature/ignixa-sdk/l1-fhirpath-seam) for the Ignixa import baseline and compatibility foundation.

• Adds cross-version import parser characterization corpus and provider-path evidence for Firely/Ignixa import parsing.
• Adds deterministic SQL/Cosmos equality-boundary characterization tests for current no-op/raw-resource comparison behavior without changing production behavior.
• Adds safe, offline-by-default import baseline tooling under tools/IncludePerf with strict report comparability gates and credential-free tests.
• Documents current evidence, pending live-store limitations, and operator prerequisites without claiming production import speedups.

Work items

• ADO 184931: reusable provider compatibility suite and evidence format.
• ADO 206675: resource equality and JSON fidelity characterization.
• ADO 198708: partial baseline tooling support only; native import performance gain remains future L4 work.
• Feature 180726: https://microsofthealth.visualstudio.com/Health/_workitems/edit/180726

Validation

• Parser characterization tests across STU3/R4/R4B/R5.
• Operations module provider-path tests across STU3/R4/R4B/R5.
• SQL Server and Cosmos DB storage-boundary unit tests.
• tools\PerfTester\PerfTester.csproj build.
• tools\IncludePerf\tests\Test-ImportBaseline.ps1 in PowerShell 7/current and Windows PowerShell 5.1.
• git --no-pager diff --check HEAD.

Limitations

No real cloud benchmark endpoints or isolated live SQL/Cosmos stores were supplied. L2 provides runnable tooling, deterministic credential-free smoke/tests, and documented current comparison boundaries, but does not claim production server metrics or a native import speedup.

[Codecov Comments Bot (codecov-commenter)]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.05%. Comparing base (ccd7f9d) to head (3a5e8dc).

Additional details and impacted files

@@                           Coverage Diff                           @@
##           feature/ignixa-sdk/l1-fhirpath-seam    #5805      +/-   ##
=======================================================================
+ Coverage                                78.90%   79.05%   +0.14%     
=======================================================================
  Files                                     1024     1024              
  Lines                                    37049    37050       +1     
  Branches                                  5645     5645              
=======================================================================
+ Hits                                     29234    29289      +55     
+ Misses                                    6415     6369      -46     
+ Partials                                  1400     1392       -8     

see 13 files with indirect coverage changes

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