setRetryPolicy method
Replaces the retry policy (the settings-hub resilience flow, issue #393). Every role's cached wrapper captured the old policy at construction, so ALL of them are rebuilt — the new knobs govern the next run's retry chain; a run already streaming keeps the old one.
Implementation
void setRetryPolicy(ModelRolesRetryPolicy policy) {
config = ModelRolesConfig(
roles: config.roles,
pathOverrides: config.pathOverrides,
retry: policy,
);
_wrappers.clear();
}