feat(ui): keep one tab presentation and document the right rail tabs

Drop the four alternative strip presentations (cards-up, spine, icons,
minimal) and the icon glyphs they needed; the strip marks the rail with
data-rail-tabs so a rail without it keeps its legacy geometry. Describe
the tab strip and the desktop one-owner rule in docs/CURRENT-STATE.md.

Co-Authored-By: Claude Fable 5.1 <[email protected]>

index.html

@@ -26,7 +26,7 @@
        with the sources: src/materialSymbolsSubset.test.mjs fails when a source
        names a glyph this list is missing, because a missing glyph does not draw
        a box — the ligature never forms and the element renders the literal word. -->
-  <link href="https://fonts.googleapis.com/css2?family=Material+Symbols+Outlined:opsz,wght,FILL,GRAD@20,400,0,0&icon_names=adjust,arrow_drop_down,arrow_forward,arrow_left,arrow_right,bolt,chevron_left,chevron_right,close,close_fullscreen,cloud,dark_mode,draw,east,flare,flight,layers,layers_clear,light_mode,local_fire_department,more_horiz,my_location,navigation,normal,on,open_in_full,public,radar,radio,right_panel_close,right_panel_open,rocket_launch,satellite_alt,search,settings,skip_next,skip_previous,streetview,tune,upload_file,videocam,view_in_ar,visibility,visibility_off" rel="stylesheet" />
+  <link href="https://fonts.googleapis.com/css2?family=Material+Symbols+Outlined:opsz,wght,FILL,GRAD@20,400,0,0&icon_names=adjust,arrow_drop_down,arrow_forward,arrow_left,arrow_right,bolt,chevron_left,chevron_right,close,close_fullscreen,dark_mode,draw,east,flare,flight,layers,layers_clear,light_mode,local_fire_department,more_horiz,my_location,navigation,normal,on,open_in_full,public,radar,radio,right_panel_close,right_panel_open,rocket_launch,search,settings,skip_next,skip_previous,upload_file,videocam,view_in_ar,visibility,visibility_off" rel="stylesheet" />
 </head>
 <body>
   <!-- gev:template scene-chrome -->