Animated placeholder with Prompt suggestion for home chat input (#1706)

<!-- This is an auto-generated description by cubic. -->
## Summary by cubic
Adds an animated placeholder with rotating prompt suggestions to the
home chat input to guide users. Also introduces a small hook for the
typing effect and updates the e2e selector to handle dynamic text.

- **New Features**
- HomeChatInput shows "Ask Dyad to build" with cycling suggestions
(ecommerce store, information page, landing page).
- New useTypingPlaceholder hook for type/delete animation with
configurable speeds and pause.
- E2E test locator updated to match aria-placeholder by prefix to
support dynamic content.

<sup>Written for commit 6b8133ec9441f60909493cad3b43315348aed2d5.
Summary will update automatically on new commits.</sup>

<!-- End of auto-generated description by cubic. -->

src/components/chat/HomeChatInput.tsx

@@ -13,6 +13,7 @@ import { HomeSubmitOptions } from "@/pages/home";
 import { ChatInputControls } from "../ChatInputControls";
 import { LexicalChatInput } from "./LexicalChatInput";
 import { useChatModeToggle } from "@/hooks/useChatModeToggle";
+import { useTypingPlaceholder } from "@/hooks/useTypingPlaceholder";
 export function HomeChatInput({
   onSubmit,
 }: {
@@ -26,6 +27,13 @@ export function HomeChatInput({
   }); // eslint-disable-line @typescript-eslint/no-unused-vars
   useChatModeToggle();
 
+  const typingText = useTypingPlaceholder([
+    "an ecommerce store...",
+    "an information page...",
+    "a landing page...",
+  ]);
+  const placeholder = `Ask Dyad to build ${typingText ?? ""}`;
+
   // Use the attachments hook
   const {
     attachments,
@@ -83,7 +91,7 @@ export function HomeChatInput({
               onChange={setInputValue}
               onSubmit={handleCustomSubmit}
               onPaste={handlePaste}
-              placeholder="Ask Dyad to build..."
+              placeholder={placeholder}
               disabled={isStreaming}
               excludeCurrentApp={false}
               disableSendButton={false}