Migrate frontend to TypeScript with Deno-based tooling (#206)

Compiles assets/*.ts via sensiolabs/typescript-bundle (standalone SWC
binary) and adds Deno for formatting, linting, type-checking, and
tests, keeping the project's no-Node/npm approach intact. Wires all
four into CI, the Justfile, and the pre-commit hook.

assets/controllers/elimination_controller.ts

@@ -0,0 +1,14 @@
+import { Controller } from '@hotwired/stimulus';
+
+export default class extends Controller {
+    next(): void {
+        const currentUrl = new URL(window.location.href);
+        const pathParts = currentUrl.pathname.split('/');
+        // Remove the last segment
+        pathParts.pop();
+        // Update the pathname
+        currentUrl.pathname = pathParts.join('/');
+        // Navigate
+        window.location.href = currentUrl.href;
+    }
+}