feat(frontend): add canvas agent empty state with server-driven starters

Render a CanvasAgentEmptyState in the Agent panel that fetches localized
starter content from the new agent-starters endpoint, with local defaults
as fallback. Clicking a starter focuses the prompt composer (new focus
handle). Includes accompanying UI polish: side-nav cleanup, animated
prompt examples, and canvas panel spacing tweaks.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/ui/components/CanvasAgentEmptyState/defaults.ts

@@ -0,0 +1,55 @@
+import type { AgentStarterConfig } from "@/domain/design";
+
+type Translate = (key: string) => string;
+
+const starterPrompts = {
+  ecommerce: "Create a premium ecommerce product image for a portable espresso machine, with realistic lighting, clean composition, benefit callouts, and marketplace-ready visual hierarchy",
+  poster: "Design a bold launch poster for a new skincare product line, with strong typography, product focus, campaign headline, date, and a polished premium layout",
+  brandVisual: "Create a brand identity direction for a modern wellness drink brand, including color palette, typography mood, logo usage, packaging accents, and social-ready visual elements",
+  socialMedia: "Create a square Instagram promotion for a weekend fashion sale, with product cutouts, discount headline, brand colors, and a layout that works as a paid social ad",
+  logo: "Design a clean vector logo for a direct-to-consumer home goods brand named Loom & Line, with a simple mark, balanced wordmark, and clear black-and-white usage"
+} as const;
+
+export function defaultAgentStarterConfig(t: Translate): AgentStarterConfig {
+  return {
+    title: t("agentEmptyTitle"),
+    description: t("agentEmptyDescription"),
+    previewImages: [
+      "https://static.codia.ai/public/images/f788bdcc/lg.webp",
+      "https://static.codia.ai/public/images/ec25067a/lg.webp",
+      "https://static.codia.ai/public/images/d4ccbe39/lg.webp"
+    ],
+    starters: [
+      { id: "ecommerce", label: t("agentStarterEcommerce"), prompt: starterPrompts.ecommerce },
+      { id: "poster", label: t("agentStarterPoster"), prompt: starterPrompts.poster },
+      { id: "brand-visual", label: t("agentStarterBrandVisual"), prompt: starterPrompts.brandVisual },
+      { id: "social-media", label: t("agentStarterSocialMedia"), prompt: starterPrompts.socialMedia },
+      { id: "logo", label: t("agentStarterLogo"), prompt: starterPrompts.logo }
+    ]
+  };
+}
+
+export function normalizeAgentStarterConfig(config: AgentStarterConfig, fallback: AgentStarterConfig): AgentStarterConfig {
+  const previewImages = Array.isArray(config.previewImages) ? config.previewImages.map((image) => image.trim()).filter(Boolean).slice(0, 3) : [];
+  const seen = new Set<string>();
+  const starters = Array.isArray(config.starters)
+    ? config.starters
+        .map((starter) => ({
+          id: starter.id.trim(),
+          label: starter.label.trim(),
+          prompt: starter.prompt.trim()
+        }))
+        .filter((starter) => {
+          if (!starter.id || !starter.label || !starter.prompt || seen.has(starter.id)) return false;
+          seen.add(starter.id);
+          return true;
+        })
+    : [];
+
+  return {
+    title: config.title?.trim() || fallback.title,
+    description: config.description?.trim() || fallback.description,
+    previewImages: previewImages.length > 0 ? previewImages : fallback.previewImages,
+    starters: starters.length > 0 ? starters : fallback.starters
+  };
+}

frontend/src/ui/components/CanvasAgentEmptyState/index.css

@@ -0,0 +1,154 @@
+.canvas-agent-empty-state {
+  width: 100%;
+  min-height: 100%;
+  flex: 1 0 auto;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  padding: 28px 20px 36px;
+  text-align: center;
+}
+
+.canvas-agent-empty-visual {
+  height: 130px;
+  display: flex;
+  align-items: flex-end;
+  justify-content: center;
+  margin-bottom: 30px;
+}
+
+.canvas-agent-empty-image {
+  position: relative;
+  width: 80px;
+  height: 105px;
+  display: block;
+  flex: 0 0 auto;
+  overflow: hidden;
+  border: 1px solid rgba(20, 20, 20, 0.08);
+  border-radius: 12px;
+  background: #f2f2f0;
+  box-shadow: 0 12px 26px rgba(20, 20, 20, 0.14);
+}
+
+.canvas-agent-empty-image.left {
+  z-index: 1;
+  transform: rotate(-8deg);
+  transform-origin: right bottom;
+}
+
+.canvas-agent-empty-image.center {
+  z-index: 2;
+  width: 100px;
+  height: 130px;
+  margin-inline: -8px;
+}
+
+.canvas-agent-empty-image:only-child.center {
+  margin-inline: 0;
+}
+
+.canvas-agent-empty-image.right {
+  z-index: 1;
+  transform: rotate(6deg);
+  transform-origin: left bottom;
+}
+
+.canvas-agent-empty-image img {
+  width: 100%;
+  height: 100%;
+  display: block;
+  object-fit: cover;
+}
+
+.canvas-agent-empty-state h2 {
+  margin: 0 0 8px;
+  color: #202124;
+  font-size: 20px;
+  font-weight: 650;
+  line-height: 1.4;
+}
+
+.canvas-agent-empty-state p {
+  margin: 0 0 28px;
+  color: #96999f;
+  font-size: 14px;
+  font-weight: 400;
+  line-height: 1.6;
+}
+
+.canvas-agent-starters {
+  width: 100%;
+  max-width: 390px;
+  display: flex;
+  flex-wrap: wrap;
+  align-items: center;
+  justify-content: center;
+  gap: 12px;
+}
+
+.canvas-agent-starters button {
+  min-height: 42px;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  padding: 9px 20px;
+  border: 1px solid #e1e3e6;
+  border-radius: 999px;
+  color: #27282b;
+  background: #fff;
+  font: inherit;
+  font-size: 14px;
+  font-weight: 500;
+  line-height: 1.5;
+  white-space: nowrap;
+  box-shadow: 0 1px 2px rgba(20, 20, 20, 0.02);
+  transition: border-color 0.15s ease, background 0.15s ease, transform 0.15s ease;
+}
+
+.canvas-agent-starters button:hover {
+  border-color: #d5d8dc;
+  background: #f7f7f6;
+  transform: translateY(-1px);
+}
+
+.canvas-agent-starters button:focus-visible {
+  outline: 2px solid #202124;
+  outline-offset: 2px;
+}
+
+.canvas-agent-starters button:active {
+  transform: translateY(0);
+}
+
+.canvas-agent-starters button:disabled {
+  color: #a6a9ae;
+  background: #f8f8f7;
+  transform: none;
+  cursor: default;
+}
+
+@media (max-width: 480px) {
+  .canvas-agent-empty-state {
+    padding-inline: 12px;
+  }
+
+  .canvas-agent-empty-visual {
+    margin-bottom: 24px;
+  }
+
+  .canvas-agent-empty-state p {
+    margin-bottom: 22px;
+  }
+
+  .canvas-agent-starters {
+    max-width: 340px;
+    gap: 8px;
+  }
+
+  .canvas-agent-starters button {
+    min-height: 38px;
+    padding: 7px 16px;
+    font-size: 13px;
+  }
+}

frontend/src/ui/components/CanvasAgentEmptyState/index.tsx

@@ -0,0 +1,49 @@
+"use client";
+
+import type { AgentStarterConfig } from "@/domain/design";
+import { useI18n } from "@/i18n/i18n";
+import "./index.css";
+
+type CanvasAgentEmptyStateProps = {
+  config: AgentStarterConfig;
+  disabled?: boolean;
+  onSelectPrompt: (prompt: string) => void;
+};
+
+export function CanvasAgentEmptyState({ config, disabled = false, onSelectPrompt }: CanvasAgentEmptyStateProps) {
+  const { t } = useI18n();
+  const previewImages = config.previewImages.slice(0, 3);
+
+  return (
+    <section className="canvas-agent-empty-state" data-testid="canvas-agent-empty-state">
+      <div className="canvas-agent-empty-visual" aria-hidden="true">
+        {previewImages.map((src, index) => (
+          <span className={`canvas-agent-empty-image ${previewImagePosition(index, previewImages.length)}`} key={src}>
+            <img src={src} alt="" draggable={false} decoding="async" />
+          </span>
+        ))}
+      </div>
+      <h2>{config.title}</h2>
+      <p>{config.description}</p>
+      <div className="canvas-agent-starters" aria-label={t("agentEmptyStarterLabel")}>
+        {config.starters.map((starter) => (
+          <button
+            type="button"
+            key={starter.id}
+            disabled={disabled}
+            data-testid="canvas-agent-starter"
+            onClick={() => onSelectPrompt(starter.prompt)}
+          >
+            {starter.label}
+          </button>
+        ))}
+      </div>
+    </section>
+  );
+}
+
+function previewImagePosition(index: number, count: number) {
+  if (count === 1) return "center";
+  if (count === 2) return index === 0 ? "left" : "right";
+  return ["left", "center", "right"][index] ?? "center";
+}

frontend/src/ui/components/CanvasPanels/index.tsx

@@ -107,7 +107,7 @@ export function CanvasGeneratedFilesPanel({
                     onDownload(node);
                   }}
                 >
-                  <Download size={19} />
+                  <Download size={16} />
                 </button>
               </div>
             ))}

frontend/src/ui/components/PromptComposer/index.tsx

@@ -59,6 +59,7 @@ type PromptPart =
 export type PromptComposerHandle = {
   insertReference: (reference: UploadedReferenceImage) => void;
   upsertReference: (reference: UploadedReferenceImage, options?: InsertReferenceOptions) => void;
+  focus: () => void;
   isFocused: () => boolean;
   insertAnnotation: (annotation: CanvasAnnotation) => void;
   serialize: (t: Translate) => string;
@@ -833,6 +834,12 @@ export const PromptComposer = forwardRef<
     upsertReference(reference, options) {
       upsertReferenceIntoEditor(reference, options);
     },
+    focus() {
+      const editor = editorRef.current;
+      if (!editor) return;
+      editor.focus();
+      placeCaretAtEnd(editor);
+    },
     isFocused() {
       const editor = editorRef.current;
       return Boolean(editor && document.activeElement && editor.contains(document.activeElement));