fix: 修正 logo 中 N 和 G 字母造型

N 添加对角线笔画（█▄ █），G 添加内横杠（█ ▀█），
避免与 O 字母造型雷同。同步更新 ui.ts 中的硬编码 wordmark。

packages/core/test/plugin/fixtures/models-dev.json

@@ -0,0 +1,14 @@
+{
+  "acme": {
+    "id": "acme",
+    "name": "Acme",
+    "env": ["ACME_API_KEY"],
+    "models": {}
+  },
+  "local": {
+    "id": "local",
+    "name": "Local",
+    "env": [],
+    "models": {}
+  }
+}

packages/core/test/plugin/fixtures/provider-factory.ts

@@ -0,0 +1,9 @@
+export function createFixtureProvider(options: Record<string, unknown>) {
+  const captured = Object.fromEntries(Object.entries(options))
+  return Object.assign((modelID: string) => ({ modelID, options: captured }), {
+    options: captured,
+    languageModel(modelID: string) {
+      return { modelID, options: captured }
+    },
+  })
+}