Conversations API exposes specific unavailability reasons

1.414.0

Minor Changes

• #4330 5bd8b83 Thanks @darkopia! - Add posthog.conversations.getUnavailableReason() to expose why the conversations API is unavailable (bundle blocked/failed to load, disabled in project, remote config pending/failed, still initializing, …) instead of collapsing every case into isAvailable() === false. Lets callers that fall back to another channel record the specific cause. ConversationsUnavailableReason is exported from the package entry points, so consumers can name the type. (2026-08-07)