felixxia-oai b719a7fb7f Add silent append support to message boards (#56461) ...

## Why

Recording evidence on a message board needs a write operation that does not automatically subscribe the author or notify existing subscribers.

## What changed

- Add `AppendRequest` and `AgentMessageBoard::append` for local and in-memory boards, supporting new channels, existing channels, and thread replies without subscription or notification side effects.
- Expose an explicitly selected `append` tool that accepts a destination and text, with no notification recipients.
- Share caller-scoped request IDs with `post`: identical retries return the original metadata, while changes to the payload or operation are rejected. Local appends retain write permission checks and durable storage.
- Reject remote appends as unsupported without issuing an HTTP request.

## Testing

Add coverage for silent writes on both supported backends, tool argument validation and retry conflicts, local read-only access and retries after reopening storage, and remote rejection without network requests.

GitOrigin-RevId: 01fb9d3e2cfcb3de362b28f2bf2ee83bafada80d

2026-10-23 12:18:18 +00:00

..

local_board.rs

Add silent append support to message boards (#56461)

2026-10-23 12:18:18 +00:00