Tidy the bot chat: icon header controls, status in the rail, narrower thread

Drop the working-on panel. Rail rows show the bot's status line first.
The header's computer and model controls are ghost icons opening modals
that explain them, and the bot's text model, provider and computer show
under its name. The thread and composer are held to 760px.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/types/index.ts

@@ -273,7 +273,6 @@ export type PagePropsType = {
     bots?: BotWithLastMessage[] | null;
     bot?: BotWithLastMessage | null;
     bot_messages?: BotMessageWithAttachments[] | null;
-    bot_task?: BotTaskWithSteps | null;
     /**
      * The open bot's computers, the one it's on first.
      */