fix+style: homepage UX fixes and Anthropic Sans font

- Switch to Anthropic Sans + Anthropic Mono (same as rag-research-copilot)
for a dramatically more premium, refined typographic feel
- Landing page headline: 26px → 38px, tighter line-height and tracking
- Onboarding steps: always show 1/2/3 (never auto-check step 1 on landing page)
- All repos: clicking active "All repos" now toggles back to homepage (null)
- Active repo: clicking it again now goes to homepage (null) not "all"
- Delete repo: still goes to "all" (makes sense, repo is gone)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ui/src/App.jsx

@@ -728,15 +728,15 @@ export default function App() {
                       <div className="onboarding-headline">Understand any GitHub repository</div>
                       <div className="onboarding-sub">Index any public repo and ask questions about the code — architecture, data flow, classes, functions, and more.</div>
                     </div>
-                    <div className={`onboarding-step ${repos.length === 0 ? "active" : "done"}`}>
-                      <span className="step-num">{repos.length > 0 ? "✓" : "1"}</span>
+                    <div className="onboarding-step active">
+                      <span className="step-num">1</span>
                       <div>
                         <strong>Paste a GitHub URL in the sidebar</strong>
                         <p>e.g. <code>github.com/karpathy/nanoGPT</code> or <code>github.com/langchain-ai/langchain</code></p>
                         <p>The app downloads and indexes every function and class.</p>
                       </div>
                     </div>
-                    <div className={`onboarding-step ${repos.length > 0 ? "active" : ""}`}>
+                    <div className="onboarding-step">
                       <span className="step-num">2</span>
                       <div>
                         <strong>Ask anything about the repo</strong>

ui/src/components/Sidebar.jsx

@@ -437,7 +437,7 @@ export default function Sidebar({ repos, reposLoading, activeRepo, onSelectRepo,
           <div className="repo-list">
             <div
               className={`repo-item ${activeRepo === "all" ? "active" : ""}`}
-              onClick={() => onSelectRepo("all")}
+              onClick={() => onSelectRepo(activeRepo === "all" ? null : "all")}
             >
               <span className="repo-slug">All repos</span>
             </div>
@@ -449,7 +449,7 @@ export default function Sidebar({ repos, reposLoading, activeRepo, onSelectRepo,
                 <div
                   key={r.slug}
                   className={`repo-item ${activeRepo === r.slug ? "active" : ""}`}
-                  onClick={() => onSelectRepo(activeRepo === r.slug ? "all" : r.slug)}
+                  onClick={() => onSelectRepo(activeRepo === r.slug ? null : r.slug)}
                 >
                   <div className="repo-item-main">
                     <span className="repo-slug">{r.slug}</span>

ui/src/index.css

@@ -8,7 +8,27 @@
            Warmer and earthier than amber, more "drawn" than digital.
    Every surface is slightly warm — no cold values anywhere.
    ════════════════════════════════════════════════════════════════════════ */
-@import url('https://fonts.googleapis.com/css2?family=Geist:wght@300;400;500;600;700&family=Geist+Mono:wght@400;500;600&display=swap');
+@font-face {
+  font-family: "Anthropic Sans";
+  src: url(https://cdn.prod.website-files.com/67ce28cfec624e2b733f8a52/69971a00a3295036497e1a28_AnthropicSans-Roman-Web.woff2) format("woff2");
+  font-weight: 300 800;
+  font-style: normal;
+  font-display: swap;
+}
+@font-face {
+  font-family: "Anthropic Sans";
+  src: url(https://cdn.prod.website-files.com/67ce28cfec624e2b733f8a52/69971a016067bf14b9b8f48d_AnthropicSans-Italic-Web.woff2) format("woff2");
+  font-weight: 300 800;
+  font-style: italic;
+  font-display: swap;
+}
+@font-face {
+  font-family: "Anthropic Mono";
+  src: url(https://cdn.prod.website-files.com/67ce28cfec624e2b733f8a52/69971a1438a2ed14d4acca5f_AnthropicMono-Roman-Web.woff2) format("woff2");
+  font-weight: 300 800;
+  font-style: normal;
+  font-display: swap;
+}
 
 *, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
 html { height: 100dvh; background: #1A1916; overflow: hidden; }
@@ -62,8 +82,8 @@ html { height: 100dvh; background: #1A1916; overflow: hidden; }
   --pill-bg: var(--surface-3);
 
   /* Typography */
-  --sans: "Geist", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
-  --mono: "Geist Mono", "JetBrains Mono", "Fira Code", monospace;
+  --sans: "Anthropic Sans", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
+  --mono: "Anthropic Mono", "JetBrains Mono", "Fira Code", monospace;
 
   /* Spacing (8px grid) */
   --space-1: 4px;  --space-2: 8px;  --space-3: 12px;
@@ -1254,21 +1274,22 @@ textarea:focus-visible {
   display: flex;
   flex-direction: column;
   gap: 12px;
-  max-width: 500px;
+  max-width: 540px;
   width: 100%;
 }
 
 /* Header for onboarding section */
 .onboarding-header {
   text-align: center;
-  margin-bottom: 8px;
+  margin-bottom: 16px;
 }
 
 .onboarding-headline {
-  font-size: 26px;
+  font-size: 38px;
   font-weight: 700;
-  letter-spacing: -0.04em;
-  margin-bottom: 8px;
+  letter-spacing: -0.03em;
+  line-height: 1.1;
+  margin-bottom: 12px;
   /* warm parchment → sienna — no cold grays */
   background: linear-gradient(120deg, #EDE4CE 20%, var(--accent-soft) 80%);
   -webkit-background-clip: text;
@@ -1277,9 +1298,10 @@ textarea:focus-visible {
 }
 
 .onboarding-sub {
-  font-size: 14px;
+  font-size: 15px;
   color: var(--text-2);
-  line-height: 1.6;
+  line-height: 1.65;
+  letter-spacing: -0.01em;
 }
 
 .onboarding-step {