Validates that a given integer is a valid 31-bit BIP32 non-hardened child index
(0 to 2,147,483,647) and returns it unchanged. Use this when deriving child keys
incrementally rather than from data.
Parameters
pathIndex: number
A non-negative integer within the non-hardened index range (0 to 2,147,483,647)
Returns number
The validated path index unchanged
Throws
If index is negative, non-integer, or exceeds 2,147,483,647
Validates that a given integer is a valid 31-bit BIP32 non-hardened child index (0 to 2,147,483,647) and returns it unchanged. Use this when deriving child keys incrementally rather than from data.