fix(eslint): move fixture ignore from package.json flag to eslint.config.js ignores array

Replace the --ignore-pattern CLI flag with an entry in the ignores array in
eslint.config.js where ESLint's flat config manages all ignore rules. Add
inline comment explaining that $lib/paraglide and $lib/generated are
intentionally omitted from the boundaries/elements list and treated as external.

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

frontend/eslint.config.js

@@ -13,7 +13,16 @@ const gitignorePath = fileURLToPath(new URL('./.gitignore', import.meta.url));
 
 export default defineConfig(
 	includeIgnoreFile(gitignorePath),
-	{ ignores: ['src/paraglide/**', '.svelte-kit.old/**'] },
+	{
+		ignores: [
+			'src/paraglide/**',
+			'.svelte-kit.old/**',
+			// Fixture files are intentionally invalid imports used to demonstrate
+			// that the boundaries/dependencies rule fires. Exclude them from the
+			// regular lint pass so `npm run lint` stays green.
+			'src/lib/**/__fixtures__/**'
+		]
+	},
 	js.configs.recommended,
 	...ts.configs.recommended,
 	...svelte.configs.recommended,
@@ -67,6 +76,9 @@ export default defineConfig(
 		plugins: { boundaries },
 		settings: {
 			'import/resolver': { typescript: { project: './tsconfig.json' } },
+			// $lib/paraglide and $lib/generated are intentionally omitted from the elements list —
+			// they are treated as external (third-party-like) by the rule and may be imported
+			// from any domain without restriction.
 			'boundaries/elements': [
 				{ type: 'document', pattern: 'src/lib/document/**' },
 				{ type: 'person', pattern: 'src/lib/person/**' },