[codex] Standardize report KPI precision

[aiSynergy37]

Resolves #8468.

Description

• Adds shared report KPI formatting helpers for fixed three-decimal numeric and percentage display.
• Applies the shared formatting to key report statistics that previously used mixed precisions (P0, P1, F1, F2).
• Adds a regression check that rendered key statistics use three decimal places while serialized report statistics preserve raw numeric values.

Validation

• dotnet build Report\QuantConnect.Report.csproj --no-restore --nologo -v:q -clp:ErrorsOnly -m:1 -p:UseSharedCompilation=false
• dotnet build Tests\QuantConnect.Tests.csproj --no-restore --nologo -v:q -clp:ErrorsOnly -p:RunAnalyzers=false -m:1 -p:UseSharedCompilation=false

Focused test attempted:

• dotnet test Tests\QuantConnect.Tests.csproj --no-build --nologo --filter "FullyQualifiedName~QuantConnect.Tests.Report.ReportChartTests.KeyStatisticsRenderWithThreeDecimalPlaces" -v:n

The focused test host aborted in the local environment with the existing pythonnet finalizer error: GIL must always be released, and it must be released from the same thread that acquired it.