feat: redesign chat UI

[MidnightCrowing]

A personal redesign of the chat UI that I find more usable. If it helps the community, I’d love to upstream it.

• Attachment-aware input with [[Note]] tags and cursor insertion
• Split message components; copy/delete/retry; rendered/raw toggle
• autosizing textarea (1–10 lines)
• Auto-scroll on load and conversation switch; linked notes open/reuse leaf

Screenshots:

[Pierrad]

Hi @MidnightCrowing, thanks for your contribution, I've tested it and it's great!

Just before merging the PR, can you translate your comments into english please? It will be easier for next contributors to understand what you did in English :)

Thanks

[MidnightCrowing]

Thanks for the feedback! I've translated all the remaining Chinese comments and messages to English.

[Pierrad]

Hi @MidnightCrowing, thanks for the edit :)

Can you rebase your changes on the latest version of the master branch please? There is major conflicts within the Message component.