feat(registry): expand antigravity model config

Remove static Name mapping and add entries for claude-sonnet-4-5,
tab_flash_lite_preview, and gpt-oss-120b-medium configs

internal/runtime/executor/antigravity_executor.go

@@ -1005,9 +1005,6 @@ func FetchAntigravityModels(ctx context.Context, auth *cliproxyauth.Auth, cfg *c
 			}
 			modelCfg := modelConfig[modelID]
 			modelName := modelID
-			if modelCfg != nil && modelCfg.Name != "" {
-				modelName = modelCfg.Name
-			}
 			modelInfo := &registry.ModelInfo{
 				ID:          modelID,
 				Name:        modelName,