fix: Add max_tokens field to all test ModelProviderInfo initializations

- Fixed all test files that initialize ModelProviderInfo
- Added max_tokens: None to maintain compatibility
- Ensures all tests compile with new max_tokens field

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

llmx-rs/core/src/config/mod.rs

@@ -2809,6 +2809,7 @@ model_verbosity = "high"
             request_max_retries: Some(4),
             stream_max_retries: Some(10),
             stream_idle_timeout_ms: Some(300_000),
+        max_tokens: None,
             requires_openai_auth: false,
         };
         let model_provider_map = {