@W-21188588 Default to ECOM Shipping when OMS does not return shipping

[sf-deepali-bharmal]

Description

Summary

When an order has OMS data but no OMS shipments (e.g. omsData.shipments is empty), the order details page now defaults to the ECOM shipment display instead of the OMS-only view.
Shoppers see the normal delivery block with Shipping Method and Shipping Address from ECOM for both single- and multi-shipment orders.

Types of Changes

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Documentation update
• Breaking change (could cause existing functionality to not work as expected)
• Other changes (non-breaking changes that does not fit any of the above)

Breaking changes include:

• Removing a public function or component or prop
• Adding a required argument to a function
• Changing the data type of a function parameter or return value
• Adding a new peer dependency to package.json

Changes

• app/pages/account/order-detail.jsx
• hasOmsShipment: New check that OMS has at least one shipment
• showShipmentsFromOmsOnly: isOmsOrder && hasOmsShipment && isMultiShipmentOrder.
• The OMS-only block (shipment methods only, no addresses) is shown only when the order has OMS data, OMS has shipments, and it's a multi-shipment order.

How to Test-Drive This PR

• Create a multi shipment order, ingest order to oms and oms not returning shipment

Checklists

General

• Changes are covered by test cases
• CHANGELOG.md updated with a short description of changes (not required for documentation updates)

Accessibility Compliance

You must check off all items in one of the follow two lists:

• There are no changes to UI

or...

• Changes were tested with a Screen Reader (iOS VoiceOver or Android Talkback) and had no issues
• Changes comply with WCAG 2.0 guidelines levels A and AA
• Changes to common UI patterns and interactions comply with WAI-ARIA best practices

Localization

• Changes include a UI text update in the Retail React App (which requires translation)

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[sf-madhuri-uppu]

Can we do the optional chaining at one place? Something like:

const shipmentCount = order?.omsData?.shipments?.length ?? 0;
const hasOmsShipment = useMemo(() => shipmentCount > 0, [shipmentCount]);

[sf-madhuri-uppu]

The name of this variable could be showMultiShipmentsFromOmsOnly