Add worktree-specific favicon branding

ui/index.html

@@ -8,10 +8,12 @@
     <meta name="apple-mobile-web-app-status-bar-style" content="black-translucent" />
     <meta name="apple-mobile-web-app-title" content="Paperclip" />
     <title>Paperclip</title>
+    <!-- PAPERCLIP_FAVICON_START -->
     <link rel="icon" href="/favicon.ico" sizes="48x48" />
     <link rel="icon" href="/favicon.svg" type="image/svg+xml" />
     <link rel="icon" type="image/png" sizes="32x32" href="/favicon-32x32.png" />
     <link rel="icon" type="image/png" sizes="16x16" href="/favicon-16x16.png" />
+    <!-- PAPERCLIP_FAVICON_END -->
     <link rel="apple-touch-icon" sizes="180x180" href="/apple-touch-icon.png" />
     <link rel="manifest" href="/site.webmanifest" />
     <script>

ui/public/worktree-favicon.svg

@@ -0,0 +1,9 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="none" stroke-linecap="round" stroke-linejoin="round">
+  <style>
+    path { stroke: #db2777; }
+    @media (prefers-color-scheme: dark) {
+      path { stroke: #f472b6; }
+    }
+  </style>
+  <path stroke-width="2" d="m16 6-8.414 8.586a2 2 0 0 0 2.829 2.829l8.414-8.586a4 4 0 1 0-5.657-5.657l-8.379 8.551a6 6 0 1 0 8.485 8.485l8.379-8.551"/>
+</svg>