[jmaeagle99]

What changed

Inbound payloads now have their external storage references resolved before decoding. When a reference is present but no external storage is configured, it is rejected with TMPRL1105 rather than silently passed through to the codec and payload converter.

• DataConverter carries an internal ExternalStorage that is propagated onto context-scoped converters.
• ExternalStorageRunner.Create returns a runner that retrieves references when storage is configured, and one that rejects them with TMPRL1105 when it is not.
• Retrieval is wired into every inbound consumption site:
  • the workflow, activity, and Nexus workers, ahead of the codec
  • the converter decode funnels (ToSingleValueAsync, ToExceptionAsync), which covers deferred paths such as memos, raw values, and failures.

Testing

• ConverterExtensionsTests covers decode funnels for reject-when-unconfigured (TMPRL1105) and retrieve-when-configured (the retrieved value surfaces through the decoded value and the reconstructed exception's details).
• ExternalStorageRunnerTests covers the Create factory: the unconfigured runner rejects references and passes plain payloads through; the configured runner retrieves.
• DataConverterTests covers ExternalStorage propagation across WithSerializationContext.
• dotnet test --filter Converters, dotnet format (whitespace + style) clean.