fix: narrow max_completion_tokens remap to explicit provider list

Address review feedback: instead of remapping max_completion_tokens
to max_tokens for all non-OpenAI providers, use an explicit allowlist
of providers known to reject max_completion_tokens. This prevents
silently breaking future providers that may support the field natively.

Signed-off-by: fre <anonwurcod@proton.me>

Author: fresh3nough

crates/goose/src/providers/openai.rs

@@ -251,8 +251,22 @@ impl OpenAiProvider {
         Self::is_responses_model(model_name)
     }
 
+    /// Providers known to reject `max_completion_tokens` and require
+    /// the legacy `max_tokens` field instead.
+    const PROVIDERS_NEEDING_MAX_TOKENS_REMAP: &[&str] = &[
+        "cerebras",
+        "custom_deepseek",
+        "groq",
+        "inception",
+        "kimi",
+        "lmstudio",
+        "mistral",
+        "moonshot",
+        "ovhcloud",
+    ];
+
     fn sanitize_request_for_compat(&self, mut payload: serde_json::Value) -> serde_json::Value {
-        if self.name == OPEN_AI_PROVIDER_NAME {
+        if !Self::PROVIDERS_NEEDING_MAX_TOKENS_REMAP.contains(&self.name.as_str()) {
             return payload;
         }
 
@@ -648,6 +662,22 @@ mod tests {
         assert!(!obj.contains_key("max_tokens"));
     }
 
+    #[test]
+    fn sanitize_noop_for_unknown_provider() {
+        let provider = make_provider("some_future_provider");
+        let payload = json!({
+            "model": "future-model",
+            "messages": [],
+            "max_completion_tokens": 16384
+        });
+
+        let result = provider.sanitize_request_for_compat(payload);
+        let obj = result.as_object().unwrap();
+
+        assert!(obj.contains_key("max_completion_tokens"));
+        assert!(!obj.contains_key("max_tokens"));
+    }
+
     #[test]
     fn sanitize_no_token_params() {
         let provider = make_provider("groq");