chore(openspec): archive add-group-buying

Sync the group-buying capability plus the order, frontend-mall, and
frontend-shop-admin requirements into the main specs, and write the capability
Purpose the archive leaves as a placeholder. This closes the last of the five
planned marketing changes.

openspec/changes/archive/2026-09-18-add-group-buying/tasks.md

@@ -2,7 +2,7 @@
 
 - [x] 1.1 Add additive migrations for shop activities, concrete groups, paid memberships, expiry/state constraints, and order group-price snapshots.
 - [x] 1.2 Implement the Rust group-buying module with shop-scoped activity management, active discovery, deterministic expiry, and open-group queries.
-- [ ] 1.3 Add shared group-buying types, checkout intent (single SKU, quantity 1), API-client methods, locales, and fixed-data adapter parity.
+- [x] 1.3 Add shared group-buying types, checkout intent (single SKU, quantity 1), API-client methods, locales, and fixed-data adapter parity.
 
 ## 2. Checkout and payment integration
 
@@ -12,11 +12,11 @@
 
 ## 3. Merchant and customer surfaces
 
-- [ ] 3.1 Add shop-admin management for activity SKU, localized presentation, price, required count, active window, group lifetime, and a group-buying nav entry.
-- [ ] 3.2 Replace the mall group-buying fixture page with live activities, open groups, paid-member counts, expiry, and open/join checkout intent; show snapshotted group prices on payment and order-detail views.
-- [ ] 3.3 Remove affected direct group-buying fixture imports while retaining fixed-data adapter support.
+- [x] 3.1 Add shop-admin management for activity SKU, localized presentation, price, required count, active window, group lifetime, and a group-buying nav entry.
+- [x] 3.2 Replace the mall group-buying fixture page with live activities, open groups, paid-member counts, expiry, and open/join checkout intent; show snapshotted group prices on payment and order-detail views.
+- [x] 3.3 Remove affected direct group-buying fixture imports while retaining fixed-data adapter support.
 
 ## 4. Verification and specification
 
-- [ ] 4.1 Seed an active deterministic group activity and browser-smoke discovery, opening, joining, and successful payment.
-- [ ] 4.2 Run cargo test for vmall-api, builds for mall and shop-admin, and strict validation for this OpenSpec change.
+- [x] 4.1 Seed an active deterministic group activity and browser-smoke discovery, opening, joining, and successful payment.
+- [x] 4.2 Run cargo test for vmall-api, builds for mall and shop-admin, and strict validation for this OpenSpec change.