refactor(storybook): consolidate dropdown stories into composed controls

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

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+PASS 24 retained Story IDs, names and tags; only approved Dropdown retirements
+PASS retained non-Overview declarations byte-identical; relocated composition separately verified
+PASS retired Dropdown IDs absent
+PASS package production source untouched
+PASS 16:9 fitted to both Inner dimensions at 1920x1080
+PASS 16:9 fitted to both Inner dimensions at 1440x900
+PASS 16:9 fitted to both Inner dimensions at 1280x720
+PASS 16:9 fitted to both Inner dimensions at 768x600
+PASS 16:9 fitted to both Inner dimensions at 390x844
+PASS 16:9 fitted to both Inner dimensions at 1000x500
+PASS one Header and no duplicate fixed Figma specimen
+PASS document selection updates Header and Callback
+PASS layer selection updates shared data
+PASS existing layer Detail callback closes list
+PASS color selection invokes host callback
+PASS line selection updates Header
+PASS ByLayer weight mode does not turn numeric property into a mode string
+PASS text style selection updates Header
+PASS dimension style selection updates Header
+PASS opening another dropdown closes the previous one
+PASS Escape closes Header dropdown
+PASS outside click closes Header dropdown
+PASS Bar Enter commits state
+PASS Bar validates min=0
+PASS Bar Escape cancels edit
+PASS Header opens panel with same Bar value
+PASS numeric weight property remains numeric after ByLayer mode
+PASS Header layer value shared with panel
+PASS panel edit updates the Bar
+PASS panel number validation rejects negative radius
+PASS panel Layer dropdown updates Header shared value
+PASS panel line dropdown updates Header shared value
+PASS panel color dropdown updates Header shared value
+PASS panel RGB validation rejects out-of-range value
+PASS gauge keyboard editing commits host state
+PASS first Escape cancels draft and retains panel
+PASS next Escape closes panel and restores Header focus
+PASS panel Close button restores focus
+PASS external Props update Bar
+PASS Bar ReadOnly
+PASS Bar Disabled
+PASS dynamic Bar field added
+PASS dynamic field shared with panel
+PASS dynamic field removed from both
+PASS shape Slot can be empty without changing panel structure
+PASS original panel size none:314x256
+PASS original panel size all:314x361
+PASS original panel size circle:314x658
+PASS original panel size expanded:314x754
+PASS expanded popup bottom accessible through internal scroll
+PASS small Inner reaches full popup bottom with native Header and popup dimensions
+PASS narrow popup Escape restores More focus
+PASS actual Storybook manager iframe fits its own Inner
+PASS no browser errors
+{"status":"PASS","checks":54,"failures":[]}