fix: upgrade devDependencies and migrate to eslint 10 flat config

- Upgrade eslint 8.31 → 10.1 with new flat config (eslint.config.js)
- Upgrade @vercel/ncc 0.36 → 0.38.4
- Replace eslint-config-airbnb-base + eslint-plugin-import with @eslint/js + @stylistic/eslint-plugin
- Remove stale overrides in package.json (word-wrap, semver)
- Remove obsolete eslint-disable comments from source files
- Add { cause } to rethrown error in rsyncCli.js
- Add .gitignore and CLAUDE.md
- Resolves all 3 npm audit vulnerabilities (flatted, minimatch, js-yaml)

eslint.config.js

@@ -0,0 +1,52 @@
+const js = require('@eslint/js');
+const stylistic = require('@stylistic/eslint-plugin');
+const globals = require('globals');
+
+module.exports = [
+  js.configs.recommended,
+  {
+    plugins: {
+      '@stylistic': stylistic
+    },
+    languageOptions: {
+      ecmaVersion: 2020,
+      sourceType: 'commonjs',
+      globals: {
+        ...globals.node,
+        ...globals.commonjs,
+        ...globals.es2020,
+        Atomics: 'readonly',
+        SharedArrayBuffer: 'readonly'
+      }
+    },
+    rules: {
+      // Stylistic rules (migrated from airbnb-base)
+      '@stylistic/comma-dangle': ['error', 'never'],
+      '@stylistic/indent': ['error', 2, { SwitchCase: 1 }],
+      '@stylistic/semi': ['error', 'always'],
+      '@stylistic/quotes': ['error', 'single', { avoidEscape: true }],
+      '@stylistic/arrow-parens': ['error', 'always'],
+      '@stylistic/brace-style': ['error', '1tbs', { allowSingleLine: true }],
+      '@stylistic/comma-spacing': ['error', { before: false, after: true }],
+      '@stylistic/key-spacing': ['error', { beforeColon: false, afterColon: true }],
+      '@stylistic/keyword-spacing': ['error', { before: true, after: true }],
+      '@stylistic/eol-last': ['error', 'always'],
+      '@stylistic/no-trailing-spaces': 'error',
+      '@stylistic/space-before-blocks': 'error',
+      '@stylistic/space-infix-ops': 'error',
+      '@stylistic/arrow-spacing': ['error', { before: true, after: true }],
+
+      // JS rules (migrated from airbnb-base)
+      'no-console': 'off',
+      'no-var': 'error',
+      'prefer-const': 'error',
+      'prefer-arrow-callback': 'error',
+      'prefer-template': 'error',
+      'object-shorthand': ['error', 'always'],
+      'no-shadow': 'error',
+      'no-use-before-define': ['error', { functions: true, classes: true, variables: true }],
+      'camelcase': ['error', { properties: 'never' }],
+      'no-unused-vars': ['error', { vars: 'all', args: 'after-used', ignoreRestSiblings: true }]
+    }
+  }
+];