fix: align vscode-ide-companion curly rule with root config (#6221)

The bare `curly: 'warn'` defaults to `'all'`, flagging single-line
guard statements (e.g. `if (!x) return;`). The root eslint.config.js
uses `['error', 'multi-line']` which only requires braces on
multi-line bodies. Align the package config to match, eliminating
10 false-positive warnings in AuthMessageHandler.ts and
settingsWriter.ts.

packages/vscode-ide-companion/eslint.config.mjs

@@ -66,7 +66,7 @@ export default [
         },
       ],
 
-      curly: 'warn',
+      curly: ['warn', 'multi-line'],
       eqeqeq: ['warn', 'always', { null: 'ignore' }],
       'no-throw-literal': 'warn',
       semi: 'warn',