fix: address Copilot review comments

- Read response.text() before JSON.parse to avoid double serialization
- Use text.slice(0, 500) instead of JSON.stringify(json).slice(0, 500)
- Add typeof content !== 'string' check for stronger type validation
- Add explicit JSON parse error handling with try/catch

packages/ai-client/src/chat.ts

@@ -30,20 +30,23 @@ export async function chat(
     body: JSON.stringify(body),
   });
 
+  const text = await res.text();
   if (!res.ok) {
-    const text = await res.text();
     throw new Error(`Chat API error ${res.status}: ${text}`);
   }
 
-  const json = (await res.json()) as {
-    choices: { message: { content: string } }[];
-  };
+  let json: { choices: { message: { content: string } }[] };
+  try {
+    json = JSON.parse(text);
+  } catch {
+    throw new Error(`Chat API returned invalid JSON: ${text.slice(0, 500)}`);
+  }
 
   // Guard against empty choices array or missing message/content fields
   const content = json.choices?.[0]?.message?.content;
-  if (content === undefined || content === null) {
+  if (typeof content !== "string") {
     throw new Error(
-      `Chat API returned no content. Response: ${JSON.stringify(json).slice(0, 500)}`
+      `Chat API returned no content. Response: ${text.slice(0, 500)}`
     );
   }
 

packages/ai-client/src/vision.ts

@@ -45,20 +45,23 @@ export async function interpretClick(
     clearTimeout(timeoutId);
   }
 
+  const text = await res.text();
   if (!res.ok) {
-    const text = await res.text();
     throw new Error(`Vision API error ${res.status}: ${text}`);
   }
 
-  const json = (await res.json()) as {
-    choices: { message: { content: string } }[];
-  };
+  let json: { choices: { message: { content: string } }[] };
+  try {
+    json = JSON.parse(text);
+  } catch {
+    throw new Error(`Vision API returned invalid JSON: ${text.slice(0, 500)}`);
+  }
 
   // Guard against empty choices array or missing message/content fields
   const content = json.choices?.[0]?.message?.content;
-  if (content === undefined || content === null) {
+  if (typeof content !== "string") {
     throw new Error(
-      `Vision API returned no content. Response: ${JSON.stringify(json).slice(0, 500)}`
+      `Vision API returned no content. Response: ${text.slice(0, 500)}`
     );
   }