Modernization and Pipeline Updates (#2468)

Migrates the Calculator release pipeline to the internal build system and modernizes the build/test toolchain alongside it.
 
 Pipelines
 - release-store.yaml: restructured so the StoreBroker payload is created and flighted inside the ReleaseStore job. The signed msixbundle is downloaded and the SB payload is created+flighted within a single job so the payload never crosses a job boundary. Added a publishToStore template parameter wired from the queue-time publishStore checkbox —  gates flight + Aero upload while always producing the SB payload artifact for inspection.
 - release-vpack.yaml: restored the vpackManifest pipeline artifact publish (lost in the OneBranch migration) using templateContext.outputs.
 - package-msixbundle.yaml: stripped of StoreBroker work; it now only bundles and signs MSIXes. ci-internal naturally skips StoreBroker.
 - Added includeX86 parameter to package-msixbundle.yaml so release.yaml can keep building the x86 Store payload while ci-internal stays x64+ARM64-only.
 - Added .config/TSAOptions.json
 - Bumped container to ltsc2025/vse2026 and agent image to windows-2025-vs2026 across release, ci-internal, and action-ci.yml.
   Refreshed the action-ci NuGet restore step and restored the x86 leg in the GitHub Actions platform and unit-test matrices.
 
 Source / project
 - Converted Calculator.sln to Calculator.slnx.
 - Refreshed SDK / toolset references across CalcManager, CalcViewModel,
   CalcViewModelCopyForUT, CalculatorUnitTests, GraphControl, GraphingImpl,
   and TraceLogging.
 - Minor target/runtime fixes in Calculator and Calculator.ManagedViewModels csproj files; package bumps in the UI
   test projects.
 - Small Settings.xaml tidy.
 - Suppressed experimental-coroutine warning in Grapher.cpp.
 
 Validation
 - GitHub Actions CI green on the branch.
 - Release pipeline succeeds end-to-end.
 - Manual smoke test of the application.