Fix hotspot counts and grouped path caps

[Widthdom]

Summary

• Keep C# property hotspots on the conservative in-target counting path so common property names are not inflated by unrelated bare-name references.
• Make hotspots --count use total-count queries for symbol, file, and grouped-name modes so --limit no longer truncates count metadata.
• Cap hotspots --group-by-name --json path samples per group and expose paths_truncated.

Validation

• dotnet test tests/CodeIndex.Tests/CodeIndex.Tests.csproj --filter FullyQualifiedName~ConsoleUiTests -p:UseSharedCompilation=false
• dotnet test tests/CodeIndex.Tests/CodeIndex.Tests.csproj --filter FullyQualifiedName~RunHotspots -p:UseSharedCompilation=false
• dotnet test tests/CodeIndex.Tests/CodeIndex.Tests.csproj --filter FullyQualifiedName~GetSymbolHotspots -p:UseSharedCompilation=false
• dotnet build CodeIndex.sln -c Release -p:UseSharedCompilation=false
• dotnet run --project tools/CodeIndex.Changelog -- check
• git diff --check
• dotnet ./src/CodeIndex/bin/Debug/net8.0/cdidx.dll status --check --json
• Codex adversarial review: No blocking/actionable issues found.

Fixes #2991
Fixes #3153
Fixes #3159