zeta: Onboarding and title bar banner (#23797)

Release Notes:

- N/A

---------

Co-authored-by: Danilo Leal <daniloleal09@gmail.com>
Co-authored-by: Danilo <danilo@zed.dev>
Co-authored-by: João Marcos <joao@zed.dev>

assets/icons/zed_predict.svg

@@ -1,5 +1,5 @@
 <svg width="16" height="16" viewBox="0 0 16 16" fill="none" xmlns="http://www.w3.org/2000/svg">
-<path d="M7 8.9V11C5.34478 11 4.65522 11 3 11V10.4L7 5.6V5H3V7.1" stroke="black" stroke-width="1.5"/>
 <path d="M12 5L14 8L12 11" stroke="black" stroke-width="1.5"/>
 <path d="M10 6.5L11 8L10 9.5" stroke="black" stroke-width="1.5"/>
+<path d="M7.5 8.9V11C5.43097 11 4.56903 11 2.5 11V10.4L7.5 5.6V5H2.5V7.1" stroke="black" stroke-width="1.5"/>
 </svg>

assets/icons/zed_predict_bg.svg

@@ -0,0 +1,19 @@
+<svg width="420" height="128" xmlns="http://www.w3.org/2000/svg">
+  <defs>
+    <pattern id="tilePattern" width="22" height="22" patternUnits="userSpaceOnUse">
+      <svg width="16" height="16" viewBox="0 0 16 16" fill="none" xmlns="http://www.w3.org/2000/svg">
+        <path d="M12 5L14 8L12 11" stroke="black" stroke-width="1.5"/>
+        <path d="M10 6.5L11 8L10 9.5" stroke="black" stroke-width="1.5"/>
+        <path d="M7.5 8.9V11C5.43097 11 4.56903 11 2.5 11V10.4L7.5 5.6V5H2.5V7.1" stroke="black" stroke-width="1.5"/>
+      </svg>
+    </pattern>
+    <linearGradient id="fade" y2="1" x2="0">
+      <stop offset="0" stop-color="white" stop-opacity=".24"/>
+      <stop offset="1" stop-color="white" stop-opacity="0"/>
+    </linearGradient>
+    <mask id="fadeMask" maskContentUnits="objectBoundingBox">
+      <rect width="1" height="1" fill="url(#fade)"/>
+    </mask>
+  </defs>
+  <rect width="100%" height="100%" fill="url(#tilePattern)" mask="url(#fadeMask)"/>
+</svg>