The raft platform plugin's check_raft_requirements() logged a WARNING every
time it returned False. Since check_fn is called on every load_gateway_config()
(~every 10s during normal gateway operation), users who don't have the raft
CLI installed get their logs flooded with no way to suppress it — hermes plugins
disable doesn't work for bundled platform plugins, and platforms.raft.enabled:
false doesn't gate the check_fn call.
Fix: make check_raft_requirements() a silent predicate (return True/False
only, no logging), matching the convention documented and used by other
platform adapters (e.g. teams/adapter.py). The caller in
gateway/platform_registry.py create_adapter() already emits its own warning
when requirements aren't met and an adapter is actually requested — that's the
correct place for a user-facing warning (fires once per connect attempt, not
once per config load).
Fixes#49234