Assert there is exactly one, rather than counting to one

[matt-edmondson]

The one finding SonarCloud left on #157 after its gate passed, in the test that PR added.

MSTEST0037 on GeneratorRegistryTests.RegisteringTwiceReplaces:

// before
Assert.AreEqual(1, SchemaGenerator.SupportedLanguages.Count(l => string.Equals(l, "fake-replaced", StringComparison.OrdinalIgnoreCase)));

// after
Assert.ContainsSingle(l => string.Equals(l, "fake-replaced", StringComparison.OrdinalIgnoreCase), SchemaGenerator.SupportedLanguages);

ContainsSingle says what the assertion means, and it reports which entries it found when there is more than one — which is precisely the failure this test exists to catch, a registration that duplicated instead of replacing. AreEqual(1, …) would only say "expected 1, was 2".

376 tests pass, 0 warnings, 0 errors.

🤖 Generated with Claude Code

https://claude.ai/code/session_01AhoPJ5AbxP8QEBNxPQYEPk

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Generated by Claude Code

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud