feat: scaffold headlamp-argocd-plugin with standard plugin structure

Adds the full plugin scaffold matching the Headlamp plugin pattern
(polaris, kube-vip, etc.):
- package.json with full devDependencies (Vitest, TypeScript, ESLint, Prettier)
- tsconfig.json, vitest.config.mts, vitest.setup.ts
- src/index.tsx with ArgoCDErrorBoundary and stub Applications route
- src/index.test.tsx smoke test to verify module importability
- CLAUDE.md documentation for future development
- .gitignore for node_modules/dist
- pnpm-lock.yaml pinned via packageManager field

ArtifactHub metadata already present (created by Hugh in PRI-186).

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

vitest.setup.ts

@@ -0,0 +1,43 @@
+import '@testing-library/jest-dom';
+
+// Node 22+ ships a minimal built-in `localStorage` global (property-bag only,
+// no getItem/setItem/removeItem/clear) that shadows jsdom's Web Storage
+// implementation. Provide a spec-compliant shim so code under test works.
+if (typeof localStorage !== 'undefined' && typeof localStorage.getItem !== 'function') {
+  const store = new Map<string, string>();
+
+  const storage = {
+    getItem(key: string): string | null {
+      return store.get(key) ?? null;
+    },
+    setItem(key: string, value: string): void {
+      store.set(key, String(value));
+    },
+    removeItem(key: string): void {
+      store.delete(key);
+    },
+    clear(): void {
+      store.clear();
+    },
+    get length(): number {
+      return store.size;
+    },
+    key(index: number): string | null {
+      return [...store.keys()][index] ?? null;
+    },
+  };
+
+  Object.defineProperty(globalThis, 'localStorage', {
+    value: storage,
+    writable: true,
+    configurable: true,
+  });
+
+  if (typeof window !== 'undefined') {
+    Object.defineProperty(window, 'localStorage', {
+      value: storage,
+      writable: true,
+      configurable: true,
+    });
+  }
+}