Fix quotes with unit multiplier

[nicholas-maestrello]

What problem is this solving?

This PR fixes critical pricing issues in the B2B Quotes GraphQL backend when applying quotes to shopping carts:

1. Index-Based Mapping Bug (Price Mismatch)

Problem: When a quote contained multiple lines of the same SKU at different prices, the useQuote mutation was using a simple index-based mapping that didn't account for VTEX's automatic item grouping. This caused:

• Wrong prices applied to wrong products
• Items merged incorrectly in the cart
• Discrepancies between quote totals and cart totals

Example:

Quote with multiple prices:
- Line 1: SKU-A, 2 units @ $1,000 (original price)
- Line 2: SKU-A, 2 units @ $800 (promotional price)
- Line 3: SKU-B, 5 units @ $500

Old behavior (index-based mapping):
1. Map by array index: [0]→$1000, [1]→$800, [2]→$500
2. VTEX groups SKU-A → creates 2 cart lines
3. Look up prices by cart index: [0]→$1000 ✅, [1]→$800 ❌ (applies to SKU-B!)
Result: SKU-B charged $800 instead of $500, promotional pricing lost

New behavior:
Cart shows:
- 2x SKU-A @ $1,000 = $2,000 (original price line)
- 2x SKU-A @ $800 = $1,600 (promotional line)
- 5x SKU-B @ $500 = $2,500
All prices correct, promotions visible!

2. Currency Precision (ORD024 Error)

Problem: VTEX's OrderForm API rejects prices that don't match the currency's decimal precision. For currencies like CLP and JPY that have 0 decimal places, prices must be multiples of 100.

Error:

ORD024 - "Precisión del precio inválida"
Item 305644: price 305644 is invalid for CLP currency

3. Gift Item Errors

Problem: The mutation attempted to apply manual prices to gift items, which is forbidden by VTEX's checkout API.

4. UnitMultiplier in Subtotals

Problem: Quote subtotal calculations weren't applying unitMultiplier, causing mismatches between displayed quote totals and actual cart totals for items sold by weight, volume, or other measurements.

---

How to test it?

Test 1: Weighted Average Pricing

1. Create a quote with multiple lines of the same SKU at different prices
2. Use GraphQL mutation:

mutation {
  useQuote(id: "quote-id")
}

3. Verify cart total matches quote subtotal (weighted average)

Test 2: CLP Currency Handling

1. Configure store to use CLP currency
2. Create quotes with various prices
3. Apply quotes and verify:
   • No ORD024 errors
   • All prices are multiples of 100

Test 3: USD/BRL Currency Handling

1. Configure store to use USD or BRL
2. Verify normal penny-precision rounding works
3. Verify weighted averages preserve cents

Test 4: Gift Items

1. Add gift items to a quote
2. Apply quote to cart
3. Verify gift items are preserved without repricing

Test 5: UnitMultiplier

1. Create quote with items that have unitMultiplier != 1 (e.g., products sold by kg)
2. Verify quote subtotal includes multiplication
3. Verify cart total matches quote subtotal

---

Screenshots or example usage

Screen.Recording.2026-02-19.at.13.19.47.mov

Related to / Depends on

• JIRA: B2BTEAM-3154
• **Companion PR

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