Fix ForceDirectedLayout.Tests CI crash: exclude native C ABI shim from code coverage

[matt-edmondson]

Problem

CI run 26700545963 failed. All 498 tests pass, but the test host for ForceDirectedLayout.Tests crashes during code-coverage teardown:

Unhandled exception. System.Exception: Pipe was disconnected.
   at Microsoft.CodeCoverage.Interprocess.LoggerClient.ReadMessageFromPipe()
   ...TestingPlatformCoverageDynamicTestSessionLifetimeHandler.OnTestSessionFinishingAsync

→ process exit 0xE0434352, test-platform exit 7, job exit 1.

It is the only test assembly referencing code with [UnmanagedCallersOnly] native entry points (NativeExports). On the .NET 10 runner the coverage engine takes that assembly down the dynamic native-instrumentation path, which crashes — consistent with the .NET 10 dynamic-native-instrumentation breaking change and microsoft/codecoverage#202.

Fix

Mark NativeExports with [ExcludeFromCodeCoverage]. Those boundary methods are reachable only via native function pointers and cannot be exercised by managed tests anyway, so excluding them keeps the coverage instrumenter away from them while preserving coverage for the rest of the engine.

Rejected alternative: setting EnableMicrosoftTestingExtensionsCodeCoverage=false on the project breaks the run a different way — CI passes --coverage to every test app, so a project without the extension fails with an unknown-option error (verified: exit 5, only 478/498 tests run).

Also suppresses two new SonarAnalyzer warnings with justifications:

• S1244 on Vec2D ==/Equals — exact equality is intentional for a blittable value type; a tolerance would break the Equals/GetHashCode contract.
• S6640 on the unsafe NativeExports class — unsafe is required for C ABI pointer marshalling.

Verification

• Clean Release build, 0 errors.
• Exact KtsuBuild test command (dotnet test --coverage --coverage-output coverage.xml --report-trx …) → 498 pass, exit 0, coverage + TRX still produced.
• ⚠️ The crash is CI-environment-specific — not reproducible locally across 6+ faithful invocations (local always uses the in-process collector). This CI run is the real verification.

🤖 Generated with Claude Code

[sonarqubecloud]

Quality Gate failed

Failed conditions
11 Security Hotspots
23.5% Coverage on New Code (required ≥ 80%)
C Security Rating on New Code (required ≥ A)

See analysis details on SonarQube Cloud

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