refactor(storybook): consolidate dropdown stories into composed controls

docs/sw/storybook-dropdown-consolidation-qa/browser-smoke.txt

@@ -0,0 +1,7 @@
+PASS 28 -> 24 SW Stories, exactly four approved Dropdown retirements
+PASS Dropdown group has only Composed Controls with original ID
+PASS all non-SW index entries identical
+PASS all retained declarations identical outside imports, meta and ComposedDemo
+PASS runtime, API, AI template, Overview, existing CSS/assets and Storybook configuration untouched
+FAIL suite completes "page.goto: net::ERR_NETWORK_ACCESS_DENIED at http://127.0.0.1:13170/iframe.html?id=sw-header--detail-buttons&viewMode=story\nCall log:\n\u001b[2m  - navigating to \"http://127.0.0.1:13170/iframe.html?id=sw-header--detail-buttons&viewMode=story\", waiting until \"load\"\u001b[22m\n\n    at go (D:\\디자인시스템\\HMDesign-SW\\packages\\sw\\tests\\dropdown-consolidation.browser.mjs:59:16)\n    at D:\\디자인시스템\\HMDesign-SW\\packages\\sw\\tests\\dropdown-consolidation.browser.mjs:65:11"
+{"status":"FAIL","checks":6,"errors":[]}