webui: Improve dx

For local development, switch to Vite and update web components for improved demo experience. Note that we haven't changed how we bundle when we're actually running in sketch; that's still the go/esbuild in-memory setup. This just changes demo dev setup to get breakpoints working and a functioning full sketch-app-shell.

We still need to add some mock data, but this is a start

- Introduced `vite.config.mts` for Vite setup with hot module reloading.
- Updated `package.json` and `package-lock.json` to include Vite and related plugins.
- Refactored demo scripts to utilize Vite for local development.
- Created `launch.json` for VSCode debugging configuration.
- Enhanced `Makefile` with a new demo task.
- Improved styling and structure in demo HTML and CSS files.
- Implemented `aggregateAgentMessages` function for message handling in web components.
diff --git a/loop/webui/src/web-components/demo/sketch-chat-input.demo.html b/loop/webui/src/web-components/demo/sketch-chat-input.demo.html
index 99d581b..e76aed7 100644
--- a/loop/webui/src/web-components/demo/sketch-chat-input.demo.html
+++ b/loop/webui/src/web-components/demo/sketch-chat-input.demo.html
@@ -2,9 +2,7 @@
   <head>
     <title>sketch-chat-input demo</title>
     <link rel="stylesheet" href="demo.css" />
-    <script
-      src="/dist/web-components/sketch-chat-input.js"
-      type="module"
+    <script type="module" src="../sketch-chat-input.ts"
     ></script>
 
     <script>