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. -->

e2e-tests/helpers/test_helper.ts

@@ -713,7 +713,7 @@ export class PageObject {
 
   getChatInput() {
     return this.page.locator(
-      '[data-lexical-editor="true"][aria-placeholder="Ask Dyad to build..."]',
+      '[data-lexical-editor="true"][aria-placeholder^="Ask Dyad to build"]',
     );
   }