fix: anthropic token count

[RogerHYang]

resolves #2414 (comment)

---

Note

Adds support for Anthropic input_tokens and output_tokens when extracting prompt and completion token counts.

• LLM token parsing:
  • Recognizes Anthropic-specific keys in token_usage:
    • Maps input_tokens to LLM_TOKEN_COUNT_PROMPT.
    • Maps output_tokens to LLM_TOKEN_COUNT_COMPLETION.

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