fix(sdk): unbreak typecheck on dev after v2 error widening (#28503)

packages/sdk/js/script/build.ts

@@ -40,6 +40,24 @@ await createClient({
   ],
 })
 
+// Patch a @hey-api/openapi-ts codegen bug: SseFn incorrectly passes the
+// endpoint's TError into the second generic of ServerSentEventsResult, which
+// is the AsyncGenerator's TReturn slot. Iterator return values have nothing
+// to do with HTTP errors, and any consumer that calls `.return()` or returns
+// from a mock generator gets type-checked against the wrong shape. Drop the
+// arg so TReturn defaults to void.
+const sseTypesPath = "./src/v2/gen/client/types.gen.ts"
+const sseTypesFile = Bun.file(sseTypesPath)
+const sseTypesSource = await sseTypesFile.text()
+const sseTypesPatched = sseTypesSource.replace(
+  "=> Promise<ServerSentEventsResult<TData, TError>>",
+  "=> Promise<ServerSentEventsResult<TData>>",
+)
+if (sseTypesPatched === sseTypesSource) {
+  throw new Error(`SseFn patch did not apply; @hey-api/openapi-ts output may have changed (${sseTypesPath})`)
+}
+await Bun.write(sseTypesPath, sseTypesPatched)
+
 await $`bun prettier --write src/gen`
 await $`bun prettier --write src/v2`
 await $`rm -rf dist`