Function debit

debit(account: AccountRef, amount: Amount): Leg
Builds a debit leg for one account. Pass the amount positive; it is stored positive. A debit lowers credit-normal accounts, such as a user's spendable balance, and raises debit-normal ones. Pairing a debit with a credit of the same amount yields stored amounts that sum to zero: a balanced posting.
Parameters
- account: AccountRef
- amount: Amount
Returns Leg
Example
```
const price = toAmount('CREDIT', 70_000n);
const legs = [
  debit(spendable('usr_buyer'), price),  // stored +70_000: buyer's balance falls
  credit(earned('usr_seller'), price),   // stored -70_000: seller's balance rises
]; // sums to zero, so the posting balances
```
- Defined in src/ledger.ts:51