chore: sync model pricing from OpenRouter API

providers/xai.toml

@@ -79,8 +79,8 @@ display_name = "Grok 3"
 tier = "frontier"
 context_window = 131072
 max_output_tokens = 32768
-input_cost_per_m = 0.3
-output_cost_per_m = 0.5
+input_cost_per_m = 3.0
+output_cost_per_m = 15.0
 supports_tools = true
 supports_vision = true
 supports_streaming = true