Enter Rillet vendor bills coded the way you always code them

**Objective:** Enter a vendor bill from `{vendor-name}` with expense number `{expense-number}` for `{amount}`, described as `{description}`, dated today unless the user says otherwise, and coded to the GL account this vendor's bills normally use.

**Step 1: Resolve the vendor**

Call `rillet-get-vendors` (it takes no filters) and find the vendor whose `name` matches `{vendor-name}`. If more than one matches, list them and stop. If none match, say so and stop; do not create a vendor.

**Step 2: Check for a duplicate**

Call `rillet-get-bills` filtered by `expense-number` = `{expense-number}`. If a bill already exists with that number, show it and stop.

**Step 3: Choose the coding**

* Call `rillet-get-bill-lines` filtered by `vendor-id` and find the `account-code` and `currency` used most often on this vendor's past bills. If there are none, use the vendor's own `account-code`, and failing that ask the user.
* Call `rillet-get-accounts` to confirm the account is active and to show its name.
* Due date: bill date plus the vendor's `payment-terms`, read as days (for example Net 30 is 30 days). If the terms cannot be read, ask.

**Step 4: Confirm, then write once**

Show the user: vendor, expense number, bill date, due date, one line with the amount, currency, account code and name, and description. Ask them to confirm or change the coding. Only after they say yes, call `rillet-add-bill` once, with `vendor-id`, `expense-number`, `bill-date`, `due-date`, `line1-amount`, `line1-currency`, `line1-account-code` and `line1-description`.

**Step 5: Verify**

Call `rillet-get-bills` filtered by `expense-number` and show the stored bill.

**Rules & Guidelines:**

* `rillet-add-bill` is the only write tool you may call, and only once, after confirmation.
* Do not call `rillet-add-vendor`, `rillet-add-account` or `rillet-update-bill`.
* If the user wants the bill split across accounts, use line 2 and line 3 of `rillet-add-bill`, and check the lines total `{amount}` before confirming.

**Validation:**

* If `{amount}` is not a positive number, ask again.
* If the coding is a guess (no past bills), say so in the confirmation.