Fix Python type hint reference edge cases

[Widthdom]

Summary

• Expand Python type hint reference extraction for ParamSpec/TypeVar/TypeVarTuple edge cases.
• Preserve comma-containing Callable annotations without treating later parameter names as type references.
• Add multiline TypeVar remapping and comment stripping for logical type factory calls.

Validation

• dotnet test tests/CodeIndex.Tests/CodeIndex.Tests.csproj --filter "FullyQualifiedName~ReferenceExtractorTests" -p:UseSharedCompilation=false --no-restore
• dotnet build CodeIndex.sln -c Release -p:UseSharedCompilation=false
• dotnet run --project tools/CodeIndex.Changelog -- check
• git diff --check
• codex exec --dangerously-bypass-approvals-and-sandbox review --base origin/main

Full dotnet test CodeIndex.sln -c Release -p:UseSharedCompilation=false --no-build was attempted and showed an existing Rust symbol extractor failure in Extract_RustTraitAssociatedTypeDefaults_RecordsPropertySymbols, unrelated to this Python reference extraction change, before the run was stopped after a long quiet period.

Documentation and changelog

• Added changelog.d/unreleased/2059.fixed.md.
• No guide or user documentation changes were needed beyond the changelog fragment because this is a reference extraction correctness fix.

Review

• Codex adversarial review found two Python reference false-positive risks.
• Both findings were addressed with targeted regression tests.

Follow-up candidates

• None.

Fixes #2059