fix(ui): add layer icon and preserve switch contrast

registry/components.json

@@ -423,6 +423,7 @@
       "variants": ["14 px", "16 px", "18 px"],
       "rules": [
         "Use semantic names from registry/icons.json.",
+        "Use layers for visibility controls of map or visual source layers; settings remains general configuration.",
         "The containing component owns surface, hit target and state; the icon owns only the glyph and uses the canonical 16 px default without an extra CSS scale.",
         "Do not copy complete Lucide or Font Awesome catalogs into an application."
       ]
@@ -501,7 +502,8 @@
         "The card owns grouping geometry but not product form schemas.",
         "Use align=center for compact result or empty messages: center the content on both axes and omit an empty body. The default start layout remains unchanged.",
         "Section and empty-state titles use the compact md token; descriptions use sm. Page/window title sizes and browser heading defaults are forbidden inside cards.",
-        "Use Switch for compact visibility/enable states; use Checker for the Engine inspector treatment."
+        "Use Switch for compact visibility/enable states; use Checker for the Engine inspector treatment.",
+        "Switch keeps its track width beside wrapped labels. The checked thumb uses on-accent contrast; the unchecked track follows theme text instead of a fixed white tint."
       ]
     },
     {