refactor(observability): add hooks.server.ts to coverage include in vite.config.ts

The handleError callback in hooks.server.ts is now gated by the 80% branch
coverage threshold along with the rest of the server-side logic.

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

frontend/vite.config.ts

@@ -71,7 +71,8 @@ export default defineConfig({
 				'src/lib/shared/utils/**',
 				'src/lib/shared/server/**',
 				'src/lib/shared/discussion/**',
-				'src/lib/document/**'
+				'src/lib/document/**',
+				'src/hooks.server.ts'
 			],
 			exclude: ['**/*.svelte', '**/*.svelte.ts', '**/__mocks__/**'],
 			thresholds: {