Surface canonical variant display_name across all variant-displaying UIs

[dougborg]

Context

After PR #N (variant card rev 2), the canonical formula for a variant's display name lives in one place — build_variant_display_name(parent_name, config_attributes, fallback_sku) -> str in katana_public_api_client/domain/variant.py. Three consumers already delegate to it:

• KatanaVariant.get_display_name (domain class)
• CachedVariant.display_name (typed-cache postprocess hook)
• VariantDetailsResponse.display_name (new field — surfaces on get_variant_details UI)

This issue tracks the audit and rollout to the other surfaces where variants appear and currently use ad-hoc name formatting (or worse, raw Variant.name).

Audit candidates

Each item below needs a check: "what does this UI currently render as the variant's title?" and "should it use display_name?"

Surface	Tool	Current behavior	Action
search_items results	search_items	Pulls from CachedVariant.display_name already, but verify it flows through the response payload	Verify
Inventory check rows	check_inventory	Per-row "name" field	Switch to display_name
Low-stock rows	list_low_stock_items	Per-row "name" field	Switch to display_name
Item detail (nested variants)	get_item	Today shows raw variant name	Switch to display_name
PO row tables (preview + result)	create_purchase_order, modify_purchase_order	row.variant_id only? Looks up names?	Determine + switch
SO row tables	create_sales_order, modify_sales_order	Same question	Determine + switch
MO row tables	create_manufacturing_order, modify_manufacturing_order	Same question	Determine + switch
MO recipe row cards	get_manufacturing_order_recipe	line items reference variants	Switch
Modification preview / result cards	Generic modify dispatcher	Diff context references variants	Switch
Fulfillment cards	fulfill_order (sales + manufacturing)	Per-row variant rendering	Switch
Receipt card	receive_purchase_order	Per-row variant rendering	Switch
Verification card	verify_order_document	line-by-line comparison	Switch

Suggested approach

1. Walk each surface, find the variant-display code path, and either:
   • Use the cache's pre-computed CachedVariant.display_name directly (cheapest — already there)
   • Compute via build_variant_display_name from the cache row's parent_name + config_attributes if the row was fetched without the precomputed field
   • Add the field to whatever response model needs it, mirroring how VariantDetailsResponse.display_name was added
2. Update tests per surface to assert the slash-joined format appears
3. Land per-surface in small PRs (one per tool family, e.g. one PR for inventory tools, one for PO/SO/MO row tables, one for fulfillment/receipt)

Acceptance criteria

• Every UI that displays a variant title uses display_name (or equivalent precomputed cache column)
• One end-to-end test per surface confirming the slash-joined format renders
• No ad-hoc string formatting like f"{parent_name} - {sku}" remaining

Related

• design(mcp): redesign Prefab UI cards across all entities for type-appropriate field hierarchy #537 (Prefab UI card redesign umbrella — this is a cross-cutting follow-up)
• The merged variant card rev 2 PR which extracts the helper and adds the field to VariantDetailsResponse