Function ensureNotNegative

ensureNotNegative(decimal: Decimal): Decimal
Ensure a value is not negative (floors at zero).
Parameters
- decimal: Decimal
  The Decimal instance to check
Returns Decimal
The original value if positive, otherwise Decimal(0)
Example
```
ensureNotNegative(toDecimal("10"));  // 10
ensureNotNegative(toDecimal("-5")); // 0
```
- Defined in packages/trading/src/utils/decimal.ts:175