Organize source files by feature

[magiccodingman]

Summary

Reorganizes the merged MagicSettings implementation into readable, navigable source files and feature folders.

The numbered Source.XX.cs files made unrelated interfaces, records, services, helpers, and tests difficult to find in Rider, GitHub, generated documentation, and AI-agent source retrieval. This PR replaces that temporary consolidated layout with a normal maintainable C# project structure.

What changed

MagicSettings

• One focused top-level type per named .cs file.
• Public contracts under Abstractions.
• Persistent configuration and composition under Configuration.
• Endpoint bootstrap and remote synchronization under ControlPlane.
• Public provenance models under Diagnostics.
• Settings attributes under Metadata.
• Migration behavior under Migrations.
• Host initialization and live runtime behavior under Runtime.
• Identity and request authentication under Security.
• On-demand secret clients under Secrets.

MagicSettings.Server

• Storage contracts under Abstractions.
• Proof verification under Authentication.
• Credential lifecycle operations under Credentials.
• Development/test stores under InMemory.
• Secret resolution under Secrets.
• Node synchronization under Synchronization.

Tests

• Configuration, security, server, and test-infrastructure classes now have descriptive filenames and feature folders.
• The unused UnitTest1.cs scaffold was removed.

Readability cleanup

• Repeated copied using blocks were replaced with project-level GlobalUsings.cs files.
• Filenames match their primary top-level types.
• Public namespaces and public APIs remain unchanged; folder organization is for navigation only.
• Added wiki/source-layout.md with placement rules to prevent numbered catch-all files from returning.
• Linked the source-layout guide from the root README and wiki index.

Behavior impact

This is a structural-only refactor. It intentionally does not change runtime behavior, protocol contracts, public namespaces, or developer-facing APIs.

Validation

GitHub Actions passed on commit aab4a1fd6db7c22ba253d5e923d6be477d2b15c2:

• dotnet restore MagicSettings/MagicSettings.sln
• dotnet build MagicSettings/MagicSettings.sln --configuration Release --no-restore
• dotnet test MagicSettings/MagicSettings.sln --configuration Release --no-build

Result: restore, Release build, and the complete xUnit test suite passed.