✨ feat(chat-input): show execution-device switcher for all agents (#15371)

✨ feat(chat-input): show execution-device switcher for all agents and add desktop download link

- Remove `!isHeterogeneous` guard so the device switcher surfaces for every agent type (not just non-heterogeneous), controlled by the existing Lab toggle
- Make the sandbox/runtime-env mode selector mutually exclusive with the device switcher: hide it when `enableExecutionDeviceSwitcher` is on
- Add a "下载桌面端 / Get Desktop App" quick link in the execution-device popover header (right side) linking to https://lobehub.com/downloads

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

locales/en-US/chat.json

@@ -217,6 +217,7 @@
   "heteroAgent.executionTarget.online": "Online",
   "heteroAgent.executionTarget.sandbox": "Cloud sandbox",
   "heteroAgent.executionTarget.sandboxDesc": "Run in an ephemeral cloud sandbox",
+  "heteroAgent.executionTarget.downloadDesktop": "Get Desktop App",
   "heteroAgent.executionTarget.title": "Execution Device",
   "heteroAgent.executionTarget.unknownDevice": "Unknown device",
   "heteroAgent.fullAccess.label": "Full access",

locales/zh-CN/chat.json

@@ -217,6 +217,7 @@
   "heteroAgent.executionTarget.online": "在线",
   "heteroAgent.executionTarget.sandbox": "云端沙箱",
   "heteroAgent.executionTarget.sandboxDesc": "在临时云端沙箱中运行",
+  "heteroAgent.executionTarget.downloadDesktop": "下载桌面端",
   "heteroAgent.executionTarget.title": "执行设备",
   "heteroAgent.executionTarget.unknownDevice": "未知设备",
   "heteroAgent.fullAccess.label": "完全访问权限",