[feat] ctrl-r to reply

Track the last person to send you a tell (assuming it's not 'someone' or 'someone powerful', or yourself), and add a hotkey shortcut 'ctrl-r' which clears the current input and inserts their name and a space plus a double quote:

e.g.
```
Atomicbob tells you, "It's not too late"
```

then pressing ctrl-r will clear the current input and set the input to: `atomicbob "` with the cursor after the '"`

Start by locating the code that handles incoming tell messages and keyboard input in the mucka repository. Implement tracking for eligible tell senders and the Ctrl-R input behavior described in the issue; done means the current input is replaced with the sender name followed by a space and an opening quote, with the cursor after the quote.

Written by the indexing model from the issue text.