Bounded data-analysis fixture

The app reads a small text fixture, sums parseable numeric values per nonblank line, and replaces output.txt in its working directory.

dotnet build DataAnalyzerReporter.csproj -c Release -m:1 -p:UseSharedCompilation=false
dotnet run --no-build -c Release --project DataAnalyzerReporter.csproj -- data.txt

Run only in a disposable copy. The stopwatch currently starts after file loading; the memory printout is a managed-memory estimate, not total allocations or peak working set. Preserve culture, parsing and output while comparing one I/O change. Do not use the historical output.txt as measured performance evidence.