Update stale API endpoints and model chains

- Instagram: migrate /v1/ to /v2/ ScrapeCreators endpoint (v1 deprecated Feb 2026)
- OpenAI: switch fallback chain to [gpt-5-mini, gpt-4.1-mini, gpt-4.1] (8x cheaper,
  gpt-5-mini is the first mini model supporting web_search with filters.allowed_domains)
- xAI: use explicit grok-4-1-fast-non-reasoning (bare name aliases to reasoning variant)
- xAI: pass from_date/to_date natively to x_search tool config instead of prompt-only
- Polymarket: correct rate limit comment (15K/10s, not 350/10s)

tests/test_models.py

@@ -84,7 +84,7 @@ class TestSelectXAIModel(unittest.TestCase):
             "fake-key",
             policy="latest"
         )
-        self.assertEqual(result, "grok-4-1-fast")
+        self.assertEqual(result, "grok-4-1-fast-non-reasoning")
 
     def test_stable_policy(self):
         # Clear cache first to avoid interference
@@ -94,7 +94,7 @@ class TestSelectXAIModel(unittest.TestCase):
             "fake-key",
             policy="stable"
         )
-        self.assertEqual(result, "grok-4-1-fast")
+        self.assertEqual(result, "grok-4-1-fast-non-reasoning")
 
     def test_pinned_policy(self):
         result = models.select_xai_model(
@@ -125,10 +125,10 @@ class TestGetModels(unittest.TestCase):
             "XAI_API_KEY": "xai-test",
         }
         mock_openai = [{"id": "gpt-5.2", "created": 1704067200}]
-        mock_xai = [{"id": "grok-4-1-fast", "created": 1704067200}]
+        mock_xai = [{"id": "grok-4-1-fast-non-reasoning", "created": 1704067200}]
         result = models.get_models(config, mock_openai, mock_xai)
         self.assertEqual(result["openai"], "gpt-5.2")
-        self.assertEqual(result["xai"], "grok-4-1-fast")
+        self.assertEqual(result["xai"], "grok-4-1-fast-non-reasoning")
 
 
 if __name__ == "__main__":