feat: c-k/c-u like readline bindings for message composer

[yilisharcs]

Problem

deleting the text from the cursor to the end of the line is cool, as is deleting the text from the cursor to the start of the line. readline. i'm not sure that this program exposes such bindings, but i would like it very much if it did, to make editing easier. there are options to bind to c-b, c-f, c-a, c-e, c-w already

Proposed solution

something that can be bound to c-k and c-u to behave as described abovee

Alternatives considered

i tried pressing c-w but it it's just not the same

Additional context

No response

Confirmations

• I searched existing issues and discussions for the same idea.
• This request does not involve self-bot automation, mass actions, or scraping.