feat(popup): validate model using structured JSON output

Replace the fire-and-forget model ping with a structured output
test that enforces a JSON schema (reply, success, data.number).
The parsed response is validated against the expected types before
showing a success message, providing stronger proof that the
selected model both responds and supports structured outputs.

src/popup/gpt-version.ts

@@ -81,12 +81,58 @@ export async function checkModel() {
       project: projectId,
       dangerouslyAllowBrowser: true
     });
-    await client.chat.completions.create({
+    const completion = await client.chat.completions.create({
       model,
-      messages: [{ role: 'user', content: 'reply just pong' }],
-      max_completion_tokens: maxTokens || 2000
+      messages: [
+        {
+          role: 'user',
+          content:
+            'reply just pong, set success to true, and provide a random number between 1 and 100.'
+        }
+      ],
+      max_completion_tokens: maxTokens || 2000,
+      response_format: {
+        type: 'json_schema',
+        json_schema: {
+          name: 'model_test',
+          strict: true,
+          schema: {
+            type: 'object',
+            properties: {
+              reply: { type: 'string', description: 'The text reply' },
+              success: { type: 'boolean', description: 'Always true' },
+              data: {
+                type: 'object',
+                properties: {
+                  number: { type: 'integer' }
+                },
+                required: ['number'],
+                additionalProperties: false
+              }
+            },
+            required: ['reply', 'success', 'data'],
+            additionalProperties: false
+          }
+        }
+      }
     });
-    showMessage({ msg: 'The model is valid!' });
+
+    const content = completion.choices[0]?.message?.content;
+    if (!content) {
+      throw new Error('No content returned from the model.');
+    }
+
+    const parsed = JSON.parse(content);
+    if (
+      typeof parsed.reply !== 'string' ||
+      typeof parsed.success !== 'boolean' ||
+      typeof parsed.data !== 'object' ||
+      typeof parsed.data.number !== 'number'
+    ) {
+      throw new Error('Model did not follow the JSON schema correctly.');
+    }
+
+    showMessage({ msg: 'The model is valid and supports structured outputs!' });
   } catch (err: any) {
     showMessage({ msg: err, isError: true });
   }