Single-call BTC macro context: price, dominance, total market cap + risk assessment.

    Use this WHENEVER analyzing any cryptocurrency (altcoin or BTC itself) to
    get the broader market frame in one shot. A SOL/ETH/whatever setup looks
    very different when BTC is dumping with rising dominance vs. when alts
    are leading. Calling this once gives Claude the macro context to provide
    Bitcoin-aware commentary alongside the per-coin analysis - without
    chaining 2-3 separate yahoo_price + manual reasoning calls.

    Returns:
      - bitcoin: price, 24h change %, volume, market cap
      - dominance: BTC and ETH market-cap share of total crypto
      - total_market: total crypto mcap + 24h change + active coin count
      - assessment: label (HIGH_RISK / ALT_RISK / ALT_FAVORABLE / OPPORTUNITY_WITH_CAUTION / NEUTRAL) + 1-paragraph reasoning