refactor: replace webpack context loading with dev server proxy

Remove the webpack-based file indexing strategy in favor of a proxy
approach. The dev server now proxies content requests to a local CLI
server, simplifying the data loading logic and removing webpack-specific
types and loaders.

src/global.d.ts

@@ -35,21 +35,6 @@ interface Window {
   ): Promise<FileSystemDirectoryHandle>;
 }
 
-interface WebpackContext {
-  (path: string): { default?: string } | string;
-  keys(): string[];
-}
-
-interface ImportMeta {
-  webpackContext(
-    directory: string,
-    options: {
-      recursive?: boolean;
-      regExp?: RegExp;
-    },
-  ): WebpackContext;
-}
-
 declare module "*.md" {
   const content: string;
   export default content;