[Feature]: Select text in chat messages with mouse + auto-copy

In the QwenPaw desktop app, you can't select text in chat messages with the mouse — clicking a message triggers a handler and prevents text selection. You have to click the copy button or use Ctrl+C every time.

Requested behavior:

1 . Select text in a message with the left mouse button (as in any normal chat UI)
2 . Selected text is automatically copied to the clipboard
3 . Paste with right-click anywhere
Basically: select → auto-copy → paste with right-click. This is standard behavior in most messengers and chat apps. Would be a great QoL improvement for QwenPaw.

Thanks!