fix(icon): clear stale glyph on name change; extract spinner color constant

Addresses review feedback:
- When `name` changes on a mounted Icon to an icon that isn't cached yet, reset
  `icon` to undefined so the reserved fallback shows instead of the previous
  glyph while the dynamic import resolves.
- Extract the fallback spinner color into a named LOADER_SPINNER_COLOR constant
  (mirrors the <Loader> default) instead of an inline magic hex.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: JeanMarcMilletScality

src/lib/components/icon/Icon.component.tsx

@@ -76,6 +76,10 @@ type Props = {
   title?: string;
 };
 
+// Mirrors the <Loader> default spinner color (see Loader.component.tsx) so the
+// fallback looks identical to a real Loader while the icon resolves.
+const LOADER_SPINNER_COLOR = '#A14FBF';
+
 // The spinner shown while a cold icon loads. Sized in em so it scales with the
 // fa-${size} font-size of the fallback box, matching the glyph it stands in for —
 // unlike <Loader>, whose container forces a fixed px svg and resets font-size.
@@ -84,7 +88,7 @@ const FallbackSpinner = styled.span`
   svg {
     width: 1em;
     height: 1em;
-    fill: #a14fbf;
+    fill: ${LOADER_SPINNER_COLOR};
   }
 `;
 
@@ -196,6 +200,10 @@ function NonWrappedIcon({
       return;
     }
 
+    // The name changed to an icon we haven't loaded yet: drop the previous glyph so the
+    // reserved fallback shows instead of a stale icon while the dynamic import resolves.
+    setIcon(undefined);
+
     // Handle FontAwesome icons with dynamic import
     import(
       /* webpackExclude: /import\.macro\.js$/ */