fix: align DeepSeek Harness model selection

DeepSeek Harness previously required a separate Runtime model selection when no administrator-provided connection was available, even if the user had already selected a compatible GoodBuddy model. It now prefers the administrator connection, then follows the compatible default model or first compatible connection across conversations, projects, and messaging channels.

Release note: 修复 DeepSeek Harness 未自动使用已选兼容模型的问题；没有管理员预置连接时，现在会跟随当前默认或首个兼容模型，无需再到 Harness 页面重复指定。

src/renderer/src/SettingsPanel.test.tsx

@@ -3057,7 +3057,9 @@ describe('SettingsPanel runtime files', () => {
     )
     expect(screen.queryByRole('radio')).not.toBeInTheDocument()
     expect(
-      screen.getByText('管理员预置的 OpenAI 兼容连接')
+      screen.getByText(
+        '自动选择：优先使用管理员预置连接，否则跟随当前兼容模型'
+      )
     ).toBeInTheDocument()
     const source = screen.getByLabelText(
       'DeepSeek Harness OpenAI 兼容模型连接'

src/renderer/src/i18n/locales/en-US/settings.ts

@@ -395,12 +395,12 @@ export const settings = {
       description:
         'GoodBuddy maintains the fixed Host and control protocol internally and uses pinned Harness libraries underneath. Ask can call native read/skill plus enabled Web Search/Fetch, while Execute can use every enabled tool and DSH plugin capability. Cancellation and workspace boundaries remain in place.',
       managedSource:
-        'Administrator-provided OpenAI-compatible connection',
+        'Automatic: prefer the administrator connection, otherwise follow a compatible current model',
       connection: 'OpenAI-compatible model connection',
       connectionPlaceholder:
-        'Select an OpenAI-compatible model connection',
+        'Automatically select a compatible model connection',
       connectionDescription:
-        'Choose a GoodBuddy model connection. It must use OpenAI Chat Completions with API-key authentication.',
+        'Optionally select a GoodBuddy model connection. Otherwise GoodBuddy uses the administrator connection, the compatible current default, or the first compatible connection. It must use OpenAI Chat Completions with API-key authentication.',
       advancedDescription:
         'This Runtime always uses GoodBuddy’s bundled, version-pinned Host and does not load user profiles or custom Hosts. GoodBuddy manages enabled marketplace plugins and loads them with the Host.',
       marketplace: {

src/renderer/src/i18n/locales/zh-CN/settings.ts

@@ -362,11 +362,12 @@ export const settings = {
       previewDescription: '开发者预览 · OpenAI 兼容',
       description:
         '由 GoodBuddy 内部维护固定 Host 与控制协议，复用锁定的 Harness 底层库；Ask 可调用 Harness 原生 read/skill 与已启用的网页搜索/抓取，Execute 可调用全部已启用工具及 DSH 插件能力，并保留取消和工作区边界。',
-      managedSource: '管理员预置的 OpenAI 兼容连接',
+      managedSource:
+        '自动选择：优先使用管理员预置连接，否则跟随当前兼容模型',
       connection: 'OpenAI 兼容模型连接',
-      connectionPlaceholder: '选择 OpenAI 兼容模型连接',
+      connectionPlaceholder: '自动选择兼容模型连接',
       connectionDescription:
-        '从 GoodBuddy 模型连接中选择；协议必须为 OpenAI Chat Completions，并使用 API Key。',
+        '可从 GoodBuddy 模型连接中显式指定；未指定时自动使用管理员预置连接、当前默认兼容连接或首个兼容连接。协议必须为 OpenAI Chat Completions，并使用 API Key。',
       advancedDescription:
         '该 Runtime 始终使用 GoodBuddy 内置并固定版本的 Host，不加载用户 profile 或自定义 Host；已启用的市场插件由 GoodBuddy 托管并随 Host 启动。',
       marketplace: {