feat: support dotted schema namespaces

[HavenDV]

Summary

• add opt-in namespace delimiter support for dotted component schema ids
• support external vs sdk-root references for excluded dotted models
• add unit and CLI integration coverage for both pipeline paths

Testing

• dotnet build AutoSDK.slnx --disable-build-servers
• dotnet test src/tests/AutoSDK.UnitTests/AutoSDK.UnitTests.csproj --disable-build-servers
• dotnet test src/tests/AutoSDK.IntegrationTests.Cli/AutoSDK.IntegrationTests.Cli.csproj --disable-build-servers
• dotnet test src/tests/AutoSDK.SnapshotTests/AutoSDK.SnapshotTests.csproj --disable-build-servers

Closes #90