Feat: Add side effect support to runtime and examples

[rian-be]

Summary

Add side effect support to the runtime audit flow and demonstrate it in the workflow approvals example.

Added

• Side effect support in mutation audit entries
• A dedicated workflow approvals scenario that prints emitted side effects
• Example side effects for workflow start and workflow rejection in WorkflowApprovals

Changed

• SideEffect.Create(...) now supports explicit RequiresAction and timestamp values
• SideEffect.Critical(...) now always marks the effect as requiring follow-up action
• Runtime audit entry creation now carries MutationResult.SideEffects through to audit records
• Runtime result logging now prints emitted side effects with severity and action flags
• The rejected workflow scenario now executes an explicit rejection path after a blocking policy decision
• ADR-006 status now reflects the accepted side effect design

Result

Side effects now move through the runtime audit path consistently and have a runnable example that shows both standard and critical effects, including the RequiresAction flag.

Testing

• dotnet build src/ModularityKit.Mutator.csproj -c Release
• dotnet build Examples/WorkflowApprovals/WorkflowApprovals.csproj -c Release

Linked Issues

• None

Checklist

• PR is focused and does not include unrelated cleanup
• Public API changes are reflected in the example and ADR
• New behavior follows the existing project structure
• I followed the Code of Conduct