CPU topology v2 phase 6: migrate profiles and core masks to CpuSelection

[PrimeBuild-pc]

Summary

Adds a conservative CpuSelection migration and compatibility layer for persisted profiles and core masks.

• Adds schema constants where legacy files without a schema version are treated as version 1 and CpuSelection-backed files are version 2.
• Adds CpuSelectionMigrationMetadata for affinity/core-mask migration provenance, confidence, topology signature, review state, and source legacy mask.
• Adds a public ProcessProfileSnapshot model with legacy ProcessorAffinity retained alongside optional CpuSelection and migration metadata.
• Extends ProfileModel and CoreMask with optional CpuSelection fields without removing existing legacy fields.
• Adds CpuSelectionMigrationService for testable migration from legacy affinity masks and bool core masks, plus safe legacy-mask build-back only when representable.
• Wires profile save/load to persist/read CpuSelection when a topology snapshot is available, while keeping legacy ProcessorAffinity for compatibility.
• Wires core mask load/save to attach CpuSelection metadata where possible while preserving BoolMask and leaving runtime core-mask apply unchanged.

Out of scope

• No UI changes.
• No profile UI migration or review UI.
• No deletion of legacy fields.
• No preset generator changes.
• No Process Lasso-style registry/IFEO work.
• No priority guardrails.
• No X3D detection.
• No version bump and no tag.
• Core mask runtime auto-apply still uses the existing legacy path; switching it to CpuSelection is left for a later phase.

Tests

• dotnet test "ThreadPilot_1.sln" --configuration Release --no-restore
• Result: 230 passed, 0 failed, 0 skipped.

Existing warnings remain in unrelated test files: CS1998 in RetryPolicyServiceTests and CS0067 in ProcessMonitorManagerServiceTests.

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 65.76087% with 63 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
Services/CoreMaskService.cs	0.00%	41 Missing ⚠️
Services/ProcessService.cs	59.09%	9 Missing ⚠️
Services/ServiceConfiguration.cs	0.00%	5 Missing ⚠️
Models/ProfileModel.cs	0.00%	4 Missing ⚠️
Models/CoreMask.cs	50.00%	3 Missing ⚠️
Services/CpuSelectionMigrationService.cs	98.88%	0 Missing and 1 partial ⚠️

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