Add webapp subproject (Vite + TypeScript + Web Components)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

webapp/src/router.ts

@@ -0,0 +1,39 @@
+type RouteHandler = (params: Record<string, string>) => void
+
+interface Route {
+  pattern: RegExp
+  keys: string[]
+  handler: RouteHandler
+}
+
+const routes: Route[] = []
+
+export function route(path: string, handler: RouteHandler): void {
+  const keys: string[] = []
+  const pattern = new RegExp(
+    '^' + path.replace(/:([^/]+)/g, (_: string, k: string) => { keys.push(k); return '([^/]+)' }) + '$'
+  )
+  routes.push({ pattern, keys, handler })
+}
+
+export function navigate(path: string): void {
+  history.pushState(null, '', path)
+  dispatch(path)
+}
+
+function dispatch(path: string): void {
+  for (const r of routes) {
+    const m = path.match(r.pattern)
+    if (m) {
+      const params: Record<string, string> = {}
+      r.keys.forEach((k, i) => { params[k] = m[i + 1] })
+      r.handler(params)
+      return
+    }
+  }
+}
+
+export function startRouter(): void {
+  window.addEventListener('popstate', () => dispatch(location.pathname))
+  dispatch(location.pathname)
+}