chore: Bump version to 0.1.9

- Wire model_max_output_tokens config to Chat Completions API
- Config takes precedence over provider default for max_tokens

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

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

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

@@ -973,6 +973,8 @@ impl Config {
 
         let mut model_providers = built_in_model_providers();
         // Merge user-defined providers into the built-in list.
+        // Note: This uses or_insert() so built-in providers take precedence.
+        // For custom max_tokens, use model_max_output_tokens config instead.
         for (key, provider) in cfg.model_providers.into_iter() {
             model_providers.entry(key).or_insert(provider);
         }