refactor(shared): simplify normalize SDK null guards

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/shared/normalize-sdk-response.ts

@@ -7,7 +7,7 @@ export function normalizeSDKResponse<TData>(
   fallback: TData,
   options?: NormalizeSDKResponseOptions,
 ): TData {
-  if (response === null || response === undefined) {
+  if (response == null) {
     return fallback
   }
 
@@ -17,7 +17,7 @@ export function normalizeSDKResponse<TData>(
 
   if (typeof response === "object" && "data" in response) {
     const data = (response as { data?: unknown }).data
-    if (data !== null && data !== undefined) {
+    if (data != null) {
       return data as TData
     }