fix: forward TResponse generic through SDK Options type for SSE endpoints
The onSseEvent callback was typed as StreamEvent<unknown> because the
response type was never threaded through the generated Options type on
the non-Nuxt path. This adds a TResponse generic to the SDK Options
type alias and forwards it to the client Options, then passes the
unwrapped response type for SSE endpoints so event.data is correctly
typed.
Closes #3463
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>