ReasoningTokens metric

@synalinks_export("synalinks.metrics.ReasoningTokens")
class ReasoningTokens(LMOperationalMetric):
    """Reasoning/thinking tokens produced during this run (Claude
    extended thinking, OpenAI o-series). Not included in the visible
    completion content but billed as output tokens.

    Example:

    ```python
    program.compile(
        metrics=[
            synalinks.metrics.ReasoningTokens(),
        ],
    )
    ```
    """

    def __init__(self, name="reasoning_tokens"):
        super().__init__(name=name)

    def result(self):
        return int(self._delta("reasoning_tokens"))