Add selected process summary to Process tab

[PrimeBuild-pc]

Summary

• Adds a lightweight SelectedProcessSummaryViewModel populated from selected ProcessModel data.
• Adds a compact Current process status strip under the Process tab process list.
• Reads memory priority once on selection when available, and checks saved persistent rule status via the existing rule store/matcher.
• Does not use PerformanceMonitoringService, start diagnostics/live monitoring, add timers, change affinity logic, or change release/version files.

Fields shown

• Selected process name and PID
• Current process status
• Executable path
• CPU priority
• Memory priority, or Memory priority unavailable
• Legacy affinity mask
• Saved rule status
• CPU usage and memory usage from ProcessModel
• Last ThreadPilot action message when available

Tests

• Added SelectedProcessSummaryViewModelTests covering no selection, selection population, selection changes, memory priority success/unavailable, no performance-monitoring dependency, no timer ownership, and persistent rule found/not found.

Validation

• dotnet test "ThreadPilot_1.sln" --configuration Release --no-restore
• Result: 314 passed, 0 failed, 0 skipped.

Limitations / next PR

• No context menu, save-as-rule flow, rules editing UI, performance graphs, diagnostics redesign, or background monitoring changes.

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 84.74576% with 27 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
ViewModels/SelectedProcessSummaryViewModel.cs	85.97%	15 Missing and 8 partials ⚠️
ViewModels/ProcessViewModel.Behaviors.partial.cs	50.00%	4 Missing ⚠️

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