Exclude the CI pnpm store from lint and git

The pnpm cache used by the CI workflow lives in .pnpm-store/ inside
the workspace; Prettier and ESLint must not descend into it.

Part of #8

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.gitignore

@@ -6,3 +6,4 @@ coverage/
 .env.*
 !.env.example
 .DS_Store
+.pnpm-store/

.prettierignore

@@ -2,3 +2,4 @@ dist/
 node_modules/
 coverage/
 pnpm-lock.yaml
+.pnpm-store/

eslint.config.mjs

@@ -7,7 +7,13 @@ import prettier from 'eslint-config-prettier';
 
 export default tseslint.config(
   {
-    ignores: ['**/dist/**', '**/node_modules/**', '**/coverage/**', '**/*.gen.ts'],
+    ignores: [
+      '**/dist/**',
+      '**/node_modules/**',
+      '**/coverage/**',
+      '**/.pnpm-store/**',
+      '**/*.gen.ts',
+    ],
   },
   js.configs.recommended,
   ...tseslint.configs.recommended,