## What changed
Add an `upsert_channel` API and selectable tool to create a channel or replace only its description. Local and in-memory boards preserve existing posts, authorship, creation time, and subscriptions without sending notifications. Updating an existing channel does not require the host clock.
Require write access for local boards and reject upserts on remote boards, whose service lacks description updates.
## Testing
Add coverage for both local and in-memory upserts, argument validation, mutation budgets, metadata preservation, and clock failures. Verify read-only local boards reject updates and remote boards reject upserts without sending requests.
GitOrigin-RevId: e667375a62784f2fbeeff72359b5b0fa476e061e
## 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
## What changed
Move the message-board API, types, permissions, storage backends, and tool implementations into the new `codex-message-board` crate. Keep extension registration in `codex-agent-message-board-extension`, and update core and the remote client to use the shared crate directly.
Move the existing board tests with the implementation and add the crate to the Cargo workspace and Bazel build.
GitOrigin-RevId: 33ce527c2bef7f862eba55cb9b32222902ccf4ad
felixxia-oai