fix(emcn): give the Geist font tokens a fallback stack

The package split replaced the auth screens' "Sim Auth Geist", Arial, sans-serif with a
bare "EMCN Geist", so sign-in, consent and docs painted in the browser's serif default until
the font loaded. The foundations sync now appends a sans or monospace fallback, and the
host bridge mirrors it.

Author: waleedlatif1

packages/emcn-platform/src/styles/host-bridge.module.css

@@ -14,7 +14,7 @@
   --design-ui-muted: rgb(10 10 10 / 60%);
   --design-ui-divider: rgb(0 0 0 / 6%);
   --design-ui-hover: rgb(10 10 10 / 6%);
-  --design-font-sans: "EMCN Geist";
+  --design-font-sans: "EMCN Geist", Arial, sans-serif;
   --design-font-weight-regular: 400;
   --design-font-weight-medium: 500;
   --design-text-body: 0.875rem;

packages/emcn/src/styles/generated/tokens.css

@@ -409,11 +409,11 @@
   --size-button-icon: var(--container-16);
   --size-button-icon-large: var(--container-20);
   --width-nav-logo: var(--container-40);
-  --font-mono: "EMCN Geist Mono";
+  --font-mono: "EMCN Geist Mono", ui-monospace, monospace;
   --font-mono-mobile: var(--font-mono);
   --font-mono-tablet: var(--font-mono);
   --font-native: system-ui, sans-serif;
-  --font-sans: "EMCN Geist";
+  --font-sans: "EMCN Geist", Arial, sans-serif;
   --font-sans-mobile: var(--font-sans);
   --font-sans-tablet: var(--font-sans);
   --text-10: 0.625rem;

scripts/sync-platform-foundations.ts

@@ -54,7 +54,9 @@ function fontFamily(value: string) {
 
 const scalable = new Set(['fontSize', 'lineHeight', 'container', 'spacing', 'breakpoint', 'radius'])
 function tokenValue(token: Token) {
-  if (token.type === 'fontFamily') return fontFamily(token.value)
+  // A fallback keeps first paint in a sans face while the self-hosted Geist loads.
+  if (token.type === 'fontFamily')
+    return `${fontFamily(token.value)}, ${token.value.includes('Mono') ? 'ui-monospace, monospace' : 'Arial, sans-serif'}`
   const size = /^(\d+(?:\.\d+)?)px$/.exec(token.value)
   return size && scalable.has(token.type) && Number(size[1]) >= 4
     ? `${Number(size[1]) / 16}rem`