Add a Go generator under sdk/typescript/gen that walks the Go types
exposed over the HTTP API and SSE stream, builds a JSON Schema for them
and emits TypeScript declarations into sdk/typescript/src/generated.
Output is committed; task check-ts fails when it drifts from the Go
source.
Runtime events now live in a single registry (pkg/runtime.EventTypes),
used by both the remote client and the generator, with a test that
every *Event struct is registered.