Fix SQL window OVER references

[Widthdom]

Summary

• Add SQL window OVER (...) clause extraction for PARTITION BY and ORDER BY identifiers.
• Suppress window function/frame syntax from being emitted as phantom call references.
• Add focused SQL reference extraction coverage and a bilingual changelog fragment.

Validation

• dotnet build
• dotnet test tests/CodeIndex.Tests/CodeIndex.Tests.csproj --filter "FullyQualifiedName~ReferenceExtractorTests.Extract_SQL"
• dotnet test tests/CodeIndex.Tests/CodeIndex.Tests.csproj --filter ReferenceExtractorTests
• dotnet run --project tools/CodeIndex.Changelog -- check
• Codex adversarial review: No blocking/actionable issues found.

Documentation and Changelog

• Added changelog.d/unreleased/2099.fixed.md.
• No README or guide updates were needed; this changes indexed SQL reference behavior without adding CLI flags or workflow contracts.

Fixes #2099

Follow-Up Candidates

• None.