feat(openai): align GPT-5.6 and Codex request contracts

crates/aether-scheduler-core/src/candidate/enumeration.rs

@@ -73,6 +73,7 @@ fn enumerate_minimal_candidate_selection_inner(
             continue;
         };
 
+        let supports_streaming = row.supports_streaming();
         candidates.push(SchedulerMinimalCandidateSelectionCandidate {
             provider_id: row.provider_id,
             provider_name: row.provider_name,
@@ -93,6 +94,7 @@ fn enumerate_minimal_candidate_selection_inner(
             global_model_id: row.global_model_id,
             global_model_name: row.global_model_name,
             selected_provider_model_name,
+            supports_streaming,
             mapping_matched_model,
         });
     }

crates/aether-scheduler-core/src/candidate/mod.rs

@@ -98,6 +98,7 @@ mod tests {
             global_model_id: format!("global-model-{id}"),
             global_model_name: "gpt-5".to_string(),
             selected_provider_model_name: "gpt-5".to_string(),
+            supports_streaming: true,
             mapping_matched_model: None,
         }
     }
@@ -211,6 +212,27 @@ mod tests {
         assert_eq!(candidates[0].selected_provider_model_name, "gpt-5-canary-1");
     }
 
+    #[test]
+    fn enumeration_preserves_effective_streaming_capability() {
+        let mut row = sample_row("1");
+        row.model_supports_streaming = Some(false);
+
+        let candidates =
+            super::enumerate_minimal_candidate_selection(EnumerateMinimalCandidateSelectionInput {
+                rows: vec![row],
+                normalized_api_format: "openai:chat",
+                requested_model_name: "gpt-5",
+                resolved_global_model_name: "gpt-5",
+                require_streaming: false,
+                required_capabilities: None,
+                auth_constraints: None,
+            })
+            .expect("candidate selection should build");
+
+        assert_eq!(candidates.len(), 1);
+        assert!(!candidates[0].supports_streaming);
+    }
+
     #[test]
     fn enumeration_preserves_theoretical_candidate_order_without_final_sorting() {
         let mut later_priority = sample_row("1");

crates/aether-scheduler-core/src/candidate/types.rs

@@ -25,6 +25,7 @@ pub struct SchedulerMinimalCandidateSelectionCandidate {
     pub global_model_id: String,
     pub global_model_name: String,
     pub selected_provider_model_name: String,
+    pub supports_streaming: bool,
     pub mapping_matched_model: Option<String>,
 }