Local slash-command results can now surface a localCommand field

What

• The final "success" result event emitted at the end of an SDK/print-mode query can now optionally include a local_command field, built from a helper call, alongside its existing fields.
• The command-dispatch return object also gained a conditional localCommand field, included only when the engine did not defer the slash command to the model (i.e. engineDeferredSlash is false).

Why This surfaces which local slash command handled a request directly in the result output, useful for SDK consumers and tooling that need to know a command was resolved locally rather than by the model.