How discovery interacts with the client-side response
cache (SEP-2549). use serves a cached tool list when one is
present and still within the server's TTL hint, refresh calls
the server and repopulates the cache, and bypass skips the
cache entirely. The cache and its per-principal isolation are
configured on the client itself (Client(cache=...)); this only
selects how discovery reads it. Defaults to use so a
configured cache is honored — note this differs from a bare
ClientGroup.list_tools(), whose own default is refresh.
