feat(settings): add model selection combobox for OpenCode agent configuration

Replace plain text inputs for model and small_model with searchable
combobox dropdowns that list models from configured providers, while
still supporting custom text entry on blur.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/i18n/messages/ar.json

@@ -555,7 +555,10 @@
       "modelId": "معرّف النموذج",
       "modelName": "اسم النموذج",
       "deleteModel": "حذف النموذج {modelId}",
-      "nativeJsonConfig": "إعداد JSON الأصلي لـ OpenCode"
+      "nativeJsonConfig": "إعداد JSON الأصلي لـ OpenCode",
+      "mainModel": "النموذج الرئيسي",
+      "smallModel": "النموذج الصغير",
+      "noMatchingModels": "لا توجد نماذج مطابقة"
     },
     "openClaw": {
       "gatewayConfig": "إعداد Gateway",

src/i18n/messages/de.json

@@ -555,7 +555,10 @@
       "modelId": "Modell-ID",
       "modelName": "Modellname",
       "deleteModel": "Modell {modelId} löschen",
-      "nativeJsonConfig": "OpenCode Native JSON-Konfiguration"
+      "nativeJsonConfig": "OpenCode Native JSON-Konfiguration",
+      "mainModel": "Hauptmodell",
+      "smallModel": "Kleines Modell",
+      "noMatchingModels": "Keine passenden Modelle"
     },
     "openClaw": {
       "gatewayConfig": "Gateway-Konfiguration",

src/i18n/messages/en.json

@@ -555,7 +555,10 @@
       "modelId": "Model ID",
       "modelName": "Model Name",
       "deleteModel": "Delete model {modelId}",
-      "nativeJsonConfig": "OpenCode Native JSON Config"
+      "nativeJsonConfig": "OpenCode Native JSON Config",
+      "mainModel": "Main Model",
+      "smallModel": "Small Model",
+      "noMatchingModels": "No matching models"
     },
     "openClaw": {
       "gatewayConfig": "Gateway Config",

src/i18n/messages/es.json

@@ -555,7 +555,10 @@
       "modelId": "ID de modelo",
       "modelName": "Nombre del modelo",
       "deleteModel": "Eliminar modelo {modelId}",
-      "nativeJsonConfig": "Configuración JSON nativa de OpenCode"
+      "nativeJsonConfig": "Configuración JSON nativa de OpenCode",
+      "mainModel": "Modelo principal",
+      "smallModel": "Modelo pequeño",
+      "noMatchingModels": "No hay modelos coincidentes"
     },
     "openClaw": {
       "gatewayConfig": "Configuración de Gateway",

src/i18n/messages/fr.json

@@ -555,7 +555,10 @@
       "modelId": "ID du modèle",
       "modelName": "Nom du modèle",
       "deleteModel": "Supprimer le modèle {modelId}",
-      "nativeJsonConfig": "Configuration JSON native OpenCode"
+      "nativeJsonConfig": "Configuration JSON native OpenCode",
+      "mainModel": "Modèle principal",
+      "smallModel": "Petit modèle",
+      "noMatchingModels": "Aucun modèle correspondant"
     },
     "openClaw": {
       "gatewayConfig": "Configuration Gateway",

src/i18n/messages/ja.json

@@ -555,7 +555,10 @@
       "modelId": "モデル ID",
       "modelName": "モデル名",
       "deleteModel": "モデル {modelId} を削除",
-      "nativeJsonConfig": "OpenCode ネイティブ JSON 設定"
+      "nativeJsonConfig": "OpenCode ネイティブ JSON 設定",
+      "mainModel": "メインモデル",
+      "smallModel": "スモールモデル",
+      "noMatchingModels": "一致するモデルがありません"
     },
     "openClaw": {
       "gatewayConfig": "Gateway 設定",

src/i18n/messages/ko.json

@@ -555,7 +555,10 @@
       "modelId": "모델 ID",
       "modelName": "모델 이름",
       "deleteModel": "모델 {modelId} 삭제",
-      "nativeJsonConfig": "OpenCode 네이티브 JSON 구성"
+      "nativeJsonConfig": "OpenCode 네이티브 JSON 구성",
+      "mainModel": "메인 모델",
+      "smallModel": "스몰 모델",
+      "noMatchingModels": "일치하는 모델 없음"
     },
     "openClaw": {
       "gatewayConfig": "Gateway 구성",

src/i18n/messages/pt.json

@@ -555,7 +555,10 @@
       "modelId": "ID do modelo",
       "modelName": "Nome do modelo",
       "deleteModel": "Excluir modelo {modelId}",
-      "nativeJsonConfig": "Configuração JSON nativa do OpenCode"
+      "nativeJsonConfig": "Configuração JSON nativa do OpenCode",
+      "mainModel": "Modelo principal",
+      "smallModel": "Modelo pequeno",
+      "noMatchingModels": "Nenhum modelo correspondente"
     },
     "openClaw": {
       "gatewayConfig": "Configuração de Gateway",

src/i18n/messages/zh-CN.json

@@ -555,7 +555,10 @@
       "modelId": "模型 ID",
       "modelName": "模型名称",
       "deleteModel": "删除模型 {modelId}",
-      "nativeJsonConfig": "OpenCode 原生 JSON 配置"
+      "nativeJsonConfig": "OpenCode 原生 JSON 配置",
+      "mainModel": "主模型",
+      "smallModel": "小模型",
+      "noMatchingModels": "没有匹配的模型"
     },
     "openClaw": {
       "gatewayConfig": "Gateway 配置",

src/i18n/messages/zh-TW.json

@@ -555,7 +555,10 @@
       "modelId": "模型 ID",
       "modelName": "模型名稱",
       "deleteModel": "刪除模型 {modelId}",
-      "nativeJsonConfig": "OpenCode 原生 JSON 配置"
+      "nativeJsonConfig": "OpenCode 原生 JSON 配置",
+      "mainModel": "主模型",
+      "smallModel": "小模型",
+      "noMatchingModels": "沒有匹配的模型"
     },
     "openClaw": {
       "gatewayConfig": "Gateway 配置",