v2.6.3

A round of fixes makes Slack-backed agents more predictable in production. The interface now gracefully falls back to public channels when the groups:read scope is missing, rather than failing outright, so agents continue to operate under reduced OAuth permissions. Read-instruction overrides have been restored and briefing guidance has been tightened, giving teams more consistent agent behavior across read and write modes. Update operations are now exposed correctly in agent mode, with agent mode returning query-only results where appropriate.

Why it matters: Slack deployments often involve carefully scoped OAuth permissions, custom briefing instructions, and a mix of agent and assistant modes. Each of these fixes removes a sharp edge that previously required workarounds, so teams running Slack agents at scale get more reliable behavior without changing their configuration.