`AgentClient.recordTokenUsage` had no `transactions` parameter, so the setting
never reached `createTransaction`, whose guard reads it from the object it is
handed. `transactions?.enabled === false` saw `undefined` and the write went
ahead.
This path is reached only from `BaseClient`'s fallback branch, when the provider
returns no usable stream usage, so the bulk path masked it wherever usage is
reported. Where it is not, the setting had no effect at all.
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