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/sketch-app-shell.css b/loop/webui/src/sketch-app-shell.css
new file mode 100644
index 0000000..57c96df
--- /dev/null
+++ b/loop/webui/src/sketch-app-shell.css
@@ -0,0 +1,22 @@
+html,
+body {
+  height: 100%;
+  overflow-y: auto;
+}
+
+body {
+  font-family:
+    system-ui,
+    -apple-system,
+    BlinkMacSystemFont,
+    "Segoe UI",
+    Roboto,
+    sans-serif;
+  margin: 0;
+  padding: 0;
+  color: #333;
+  line-height: 1.4;
+  overflow-x: hidden; /* Prevent horizontal scrolling */
+  display: flex;
+  flex-direction: column;
+}