Problem

• Service code emitted duplicate isEvent() marker methods when multiple streaming methods shared the same result type.
• JSON-RPC SSE server stream generated duplicate "case *" entries when endpoints shared the same streaming result type.

Fix

• codegen/service: Add dedupeByResult helper and use it in service.go.tpl so we only emit one Event marker per unique result type, and list unique Accepted types in the service-level Stream interface.
• jsonrpc/codegen: Add dedupeBySSEEvent in SSE server codegen and use it in sse_server_stream_impl.go.tpl to generate a single switch case per unique SSE event type.

Tests

• TestService_DedupEventMarkers: Asserts a single isEvent() marker for SharedEvent when two streaming methods share the type.
• TestJSONRPCSSE_DedupEventTypes: Asserts a single switch case for SharedSSEEvent when two JSON-RPC SSE endpoints share the type.

Both tests fail without the fix and pass with it.

Notes

• Changes are narrowly scoped to code generation; no behavior changes beyond duplicate emission removal.