swarm-ui: the egress icon is shown as an emoji like the others

The globe of the egress card and of the allowed-domains box showed as a
plain monochrome glyph where the bee and the bell were emoji: a font with a
text-style glyph for the globe won over the emoji font. The two globes now carry
the emoji variation selector, and a panel's icon asks for emoji presentation
(font-variant-emoji), so another icon cannot fall the same way.

frontend/packages/swarm-ui/src/agent/detail/AllowedDomains.tsx

@@ -196,7 +196,7 @@ export function AddForm({
   return (
     <Panel
       title={`${deny ? "denied" : "allowed"} domain — ${agent ?? "swarm-wide"}`}
-      icon="🌐"
+      icon={"🌐\uFE0F"}
       onClose={onClose}
     >
       <p>

frontend/packages/swarm-ui/src/pages/swarm/EgressCard.tsx

@@ -136,7 +136,7 @@ export function EgressCard() {
   return (
     <LazyDisclosure
       title="egress"
-      icon="🌐"
+      icon={"🌐\uFE0F"}
       hint="the domains every agent may or may not reach through its hive's proxy"
     >
       <EgressBody />

frontend/packages/swarm-ui/src/ui/panel/Panel.css

@@ -28,6 +28,9 @@
 .ui-panel-icon {
   font-size: 1.2em;
   line-height: 1;
+  /* A panel's icon is an emoji: a font that has a text-style glyph for it
+     (the globe, in some monospace fonts) must not win over the emoji font. */
+  font-variant-emoji: emoji;
 }
 /* `margin-left: auto` (not `justify-content: space-between` on the
    header) so this cluster still lands at the right edge even on the