New thread opens in the main view

Picking New thread from the ✨ menu used to open the chat side panel. It now opens the composer in the main view — the full-width surface — and closes the side panel on the way, so you are never looking at two separate places to start a conversation.

This also fixes a case where the menu entry appeared to do nothing at all: when the side panel was closed, the signal telling the composer to start fresh was sent before there was anything listening for it, and it was simply lost. That path is gone.

The entry is now marked with a plain ➕ rather than a chat bubble. A plus reads as "new" in every language and no longer looks identical to the Threads entry right below it.

On your home page, My items now sits above Open threads.