Stoat eats the first letter of the message, if holding shift

### What happened?

When you start typing with the chatbox not selected and hold shift, for capitalizing the first letter of the sentence as is common, stoat will skip the first letter
This is rather annoying

```
AMD Ryzen 9 5950X (32) @ 5.09 GHz
AMD Radeon RX 6900 XT [Discrete]
32GB RAM
64GB Swap
NixOS 25.11 (Xantusia) x86_64
Linux 6.18.13-zen1
KDE Plasma
KWin (Wayland)
```