🤖 feat: add Geist font for Windows/Linux (#580)

This PR updates the font configuration to use San Francisco on macOS and
Geist on Windows/Linux.

## Changes

- Installed `geist` package and bundled Geist Sans and Geist Mono
variable fonts
- Added @font-face declarations for both fonts in `globals.css`
- Updated `--font-primary` to prefer `-apple-system` (San Francisco)
first, then fall back to `Geist`
- Updated `--font-monospace` to prefer macOS system monospace fonts,
then `Geist Mono`

## Implementation

The font-family stack now works as follows:
- **macOS**: Uses `-apple-system` (San Francisco) for UI and
`Monaco`/`Menlo` for monospace
- **Windows/Linux**: Falls through to `Geist` for UI and `Geist Mono`
for monospace

Font files are bundled in `public/fonts/` and loaded with `font-display:
swap` for better performance.

_Generated with `mux`_

Author: kylecarbs

.gitignore

@@ -1,3 +1,6 @@
+# Font files (copied from node_modules during build)
+public/fonts/
+
 # OSX
 .DS_Store
 

Makefile

@@ -145,6 +145,7 @@ build-renderer: node_modules/.installed src/version.ts ## Build renderer process
 build-static: ## Copy static assets to dist
 	@echo "Copying static assets..."
 	@mkdir -p dist
+	@./scripts/copy-fonts.sh
 	@cp static/splash.html dist/splash.html
 	@cp -r public/* dist/
 

bun.lock

@@ -126,6 +126,7 @@
     "eslint-plugin-react-hooks": "^5.2.0",
     "eslint-plugin-storybook": "10.0.0",
     "eslint-plugin-tailwindcss": "4.0.0-beta.0",
+    "geist": "^1.5.1",
     "jest": "^30.1.3",
     "mermaid": "^11.12.0",
     "nodemon": "^3.1.10",

package.json

@@ -0,0 +1,18 @@
+#!/usr/bin/env bash
+# Copy Geist fonts from node_modules to public/fonts
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_ROOT="$(cd "${SCRIPT_DIR}/.." && pwd)"
+
+mkdir -p "${PROJECT_ROOT}/public/fonts/geist-sans"
+mkdir -p "${PROJECT_ROOT}/public/fonts/geist-mono"
+
+# Copy variable fonts (support weights 100-900)
+cp "${PROJECT_ROOT}/node_modules/geist/dist/fonts/geist-sans/Geist-Variable.woff2" \
+  "${PROJECT_ROOT}/public/fonts/geist-sans/"
+
+cp "${PROJECT_ROOT}/node_modules/geist/dist/fonts/geist-mono/GeistMono-Variable.woff2" \
+  "${PROJECT_ROOT}/public/fonts/geist-mono/"
+
+echo "✓ Copied Geist variable fonts to public/fonts/"

public/fonts/geist-mono/GeistMono-Variable.woff2

@@ -1,6 +1,23 @@
 @import "tailwindcss";
 @source "../node_modules/streamdown/dist/index.js";
 
+/* Geist Font Declarations */
+@font-face {
+  font-family: "Geist";
+  src: url("/fonts/geist-sans/Geist-Variable.woff2") format("woff2");
+  font-weight: 100 900;
+  font-style: normal;
+  font-display: swap;
+}
+
+@font-face {
+  font-family: "Geist Mono";
+  src: url("/fonts/geist-mono/GeistMono-Variable.woff2") format("woff2");
+  font-weight: 100 900;
+  font-style: normal;
+  font-display: swap;
+}
+
 @theme {
   /* Mode Colors */
   --color-plan-mode: hsl(210 70% 40%);
@@ -205,15 +222,16 @@
   --color-token-cached: hsl(0 0% 50%);
 
   /* Font Variables */
-  /* Primary UI Font - System fonts for best native appearance */
+  /* Primary UI Font - San Francisco on macOS, Geist on Windows/Linux */
   --font-primary:
-    system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Helvetica Neue", Arial,
-    sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
+    -apple-system, BlinkMacSystemFont, "Geist", system-ui, "Segoe UI", "Roboto",
+    "Helvetica Neue", Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji",
+    "Segoe UI Symbol";
 
-  /* Monospace Font - Code and technical content */
+  /* Monospace Font - System monospace on macOS, Geist Mono on Windows/Linux */
   --font-monospace:
-    "Monaco", "Menlo", "Ubuntu Mono", "Consolas", "Courier New", monospace, "Apple Color Emoji",
-    "Segoe UI Emoji", "Segoe UI Symbol";
+    "Monaco", "Menlo", "Geist Mono", "Ubuntu Mono", "Consolas", "Courier New", monospace,
+    "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
 }
 
 body {