docs(21-02): complete candidate detail page and thread modal plan

- Add 21-02-SUMMARY.md with execution results
- Update STATE.md, ROADMAP.md, REQUIREMENTS.md

.planning/ROADMAP.md

@@ -57,7 +57,7 @@
 - [x] **Phase 18: Global Items & Public Profiles** — Global item catalog, user profiles, and public setup sharing (completed 2026-04-05)
 - [x] **Phase 19: Reference Item Model & Tags Schema** — Collection items as references to global catalog, tag system for discovery (completed 2026-04-05)
 - [x] **Phase 20: FAB & Full-Screen Catalog Search** — Global FAB with mini menu, full-screen catalog search with tag filtering (completed 2026-04-06)
-- [ ] **Phase 21: Item & Catalog Detail Pages** — Full detail pages for collection items and catalog entries, replacing slide-out panels
+- [x] **Phase 21: Item & Catalog Detail Pages** — Full detail pages for collection items and catalog entries, replacing slide-out panels (completed 2026-04-06)
 - [ ] **Phase 22: Add-from-Catalog & Thread Integration** — Add catalog items to collection and threads, resolution creates reference items
 - [ ] **Phase 23: Manual Entry Fallback** — Manual add for items not in catalog, non-functional submission prompt
 
@@ -266,6 +266,6 @@ Plans:
 | 18. Global Items & Public Profiles | v2.0 | 4/5 | Complete    | 2026-04-05 |
 | 19. Reference Item Model & Tags Schema | v2.0 | 3/3 | Complete    | 2026-04-05 |
 | 20. FAB & Full-Screen Catalog Search | v2.0 | 2/2 | Complete    | 2026-04-06 |
-| 21. Item & Catalog Detail Pages | v2.0 | 0/? | Not started | - |
+| 21. Item & Catalog Detail Pages | v2.0 | 1/1 | Complete   | 2026-04-06 |
 | 22. Add-from-Catalog & Thread Integration | v2.0 | 0/? | Not started | - |
 | 23. Manual Entry Fallback | v2.0 | 0/? | Not started | - |