Feat: Strengthen governance runtime concurrency and resolution

[rian-be]

Summary

Strengthen governance runtime semantics around request concurrency and version aware resolution.

Added

• optimistic concurrency revision support for governed mutation requests
• explicit governance storage contract with Create(...) and TryStore(..., expectedRevision)
• MutationRequestAlreadyExistsException for duplicate request creation attempts
• MutationRequestConcurrencyException for stale lifecycle and resolution writes
• persisted version resolution path through IMutationRequestVersionResolutionManager
• MutationRequestVersionResolutionManager.ResolveAndStore(...)
• expanded resolution runtime helpers for version evaluation and state composition
• governance regression coverage for stale lifecycle transitions, guarded storage updates, and persisted resolution outcomes

Changed

• governance lifecycle transitions now persist through compare and swap semantics instead of blind save flow
• in-memory governance storage now rejects duplicate creates and stale revision writes
• version-aware governance resolution can now run through a canonical persisted runtime path instead of relying only on in-memory caller handling
• governance examples now show persisted resolution usage in addition to pure evaluator usage

Result

Governance runtime now has explicit optimistic concurrency semantics for request lifecycle and storage, and version-aware resolution outcomes can be persisted through a canonical runtime path. Stale transitions no longer succeed silently, and version resolution decisions are no longer easy to lose through caller misuse.

Testing

• dotnet build src/ModularityKit.Mutator.Governance.csproj -c Release
• dotnet test Tests/ModularityKit.Mutator.Governance.Tests/ModularityKit.Mutator.Governance.Tests.csproj -c Release
• dotnet build Examples/Governance/VersionedResolution/VersionedResolution.csproj -c Release

Linked Issues

• Closes [Task]: Persist governance version resolution outcomes through runtime #12

Checklist

• lifecycle transitions reject stale concurrent writes
• governance storage uses explicit create and guarded update semantics
• version resolution has a persisted runtime path
• examples and tests cover the new governance runtime behavior