perf: subset the icon font and drop the unused second family (#513)

Supersedes #239 by @mml-studio, ported onto the current component layout with fixes from review.

Verified before merge: format, package boundaries, unit suite, build, and the browser tracking suite; a browser harness for the change where one applies; adversarial review applied.

Co-authored-by: Memel <[email protected]>

index.html

@@ -9,8 +9,11 @@
   <link rel="preconnect" href="https://fonts.googleapis.com" />
   <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin />
   <link href="https://fonts.googleapis.com/css2?family=JetBrains+Mono:wght@300;400;500;600;700&family=Inter:wght@300;400;500;600&display=swap" rel="stylesheet" />
-  <link href="https://fonts.googleapis.com/css2?family=Material+Symbols+Outlined:opsz,wght,FILL,GRAD@20,400,0,0" rel="stylesheet" />
-  <link href="https://fonts.googleapis.com/icon?family=Material+Icons+Round" rel="stylesheet" />
+  <!-- Icon font subset to the glyphs this app renders. Keep `icon_names` in sync
+       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,dark_mode,draw,east,flare,flight,layers_clear,light_mode,local_fire_department,my_location,navigation,normal,on,open_in_full,public,radar,radio,right_panel_close,right_panel_open,rocket_launch,skip_next,skip_previous,view_in_ar" rel="stylesheet" />
 </head>
 <body>
   <!-- gev:template scene-chrome -->