Group chats: rail background

A

Why the rail stayed plain

The rail backdrop (#895) stored one bot colour and read the global background setting. Only the single-bot chat and the bot page sent it a colour. The group chat never did, so the rail stayed plain next to it.

B

Fix

Piece	Change
`RailBackdrop.tsx`	The store now keeps a list of colours plus the background of the screen that sent them
`GroupChatView.tsx`	Sends the members' colours and the group's background setting, so turning backgrounds off for group chats is respected
Desktop rail + phone/PWA drawer	No change. Both already read from the same store
Docs	`surfaces/bots.mdx` now describes the sidebar background

C

Status

Merged 2026-10-29: allternit-ai #899 (ab739bc) and platform #1972 (e356181).
The ai main merge automatically deploys ai.allternit.com and the m.allternit.com app. Desktop gets it with the next runtime publish.
I haven't looked at it in the running app yet.

# Group chats: rail background

## Why the rail stayed plain
The rail backdrop (#895) stored one bot colour and read the global background setting. Only the single-bot chat and the bot page sent it a colour. The group chat never did, so the rail stayed plain next to it.

## Fix
| Piece | Change |
|---|---|
| `RailBackdrop.tsx` | The store now keeps a list of colours plus the background of the screen that sent them |
| `GroupChatView.tsx` | Sends the members' colours and the group's background setting, so turning backgrounds off for group chats is respected |
| Desktop rail + phone/PWA drawer | No change. Both already read from the same store |
| Docs | `surfaces/bots.mdx` now describes the sidebar background |

## Status
- **Merged** 2026-10-29: allternit-ai #899 (`ab739bc`) and platform #1972 (`e356181`).
- The ai main merge automatically deploys ai.allternit.com and the m.allternit.com app. Desktop gets it with the next runtime publish.
- I haven't looked at it in the running app yet.