refactor(api): move Codex client model handling to registry package

- Relocated Codex client model JSON and related logic from `openai` package to `registry` for better modularity.
- Updated references to use `registry.GetCodexClientModelsJSON()` in loading logic.
- Extended test cases to cover additional field removals (`upgrade`, `availability_nux`).

internal/api/server_test.go

@@ -346,6 +346,12 @@ func TestModelsWithClientVersionReturnsCodexCatalog(t *testing.T) {
 	if _, ok := custom["apply_patch_tool_type"]; ok {
 		t.Fatal("expected custom model to omit apply_patch_tool_type")
 	}
+	if _, ok := custom["upgrade"]; ok {
+		t.Fatal("expected custom model to omit upgrade")
+	}
+	if _, ok := custom["availability_nux"]; ok {
+		t.Fatal("expected custom model to omit availability_nux")
+	}
 
 	hiddenModels := map[string]bool{
 		"grok-imagine-image-quality": false,

internal/registry/codex_client_models.go

@@ -0,0 +1,11 @@
+package registry
+
+import _ "embed"
+
+//go:embed models/codex_client_models.json
+var codexClientModelsJSON []byte
+
+// GetCodexClientModelsJSON returns the embedded Codex client model catalog.
+func GetCodexClientModelsJSON() []byte {
+	return append([]byte(nil), codexClientModelsJSON...)
+}

sdk/api/handlers/openai/codex_client_models.go

@@ -66,7 +66,7 @@ func buildCodexClientModels(models []map[string]any) []map[string]any {
 func loadCodexClientModelTemplates() (map[string]map[string]any, map[string]any, error) {
 	codexClientModelTemplatesOnce.Do(func() {
 		var payload codexClientModelsPayload
-		codexClientModelTemplatesErr = json.Unmarshal(codexClientModelsJSON, &payload)
+		codexClientModelTemplatesErr = json.Unmarshal(registry.GetCodexClientModelsJSON(), &payload)
 		if codexClientModelTemplatesErr != nil {
 			return
 		}
@@ -120,6 +120,8 @@ func applyCodexClientModelMetadata(entry map[string]any, id string, model map[st
 	entry["priority"] = 100
 	entry["prefer_websockets"] = false
 	delete(entry, "apply_patch_tool_type")
+	delete(entry, "upgrade")
+	delete(entry, "availability_nux")
 
 	if contextWindow > 0 {
 		entry["context_window"] = contextWindow

sdk/api/handlers/openai/openai_handlers.go

@@ -8,7 +8,6 @@ package openai
 
 import (
 	"context"
-	_ "embed"
 	"encoding/json"
 	"fmt"
 	"net/http"
@@ -30,9 +29,6 @@ type OpenAIAPIHandler struct {
 	*handlers.BaseAPIHandler
 }
 
-//go:embed codex_client_models.json
-var codexClientModelsJSON []byte
-
 // NewOpenAIAPIHandler creates a new OpenAI API handlers instance.
 // It takes an BaseAPIHandler instance as input and returns an OpenAIAPIHandler.
 //