Function parse_spot_instruments 

pub fn parse_spot_instruments(
    meta: &SpotMeta,
) -> Result<Vec<HyperliquidInstrumentDef>, String>

Parse spot instrument definitions from Hyperliquid spotMeta response.

Hyperliquid spot follows these rules:

• Price decimals = max(0, 8 - base_sz_decimals) per venue docs
• Size decimals from base token
• All pairs in the universe are active, including non-canonical pairs