🔧 Replace ESLint and Prettier with oxlint and oxfmt

- Drop .eslintrc.cjs and .prettierrc, add .oxlintrc.json and .oxfmtrc.json
- oxlint covers correctness/suspicious/perf/style/restriction categories
  plus import and typescript plugins; oxfmt reads the same .prettierrc-style
  options we had before
- Update lefthook.yml pre-commit jobs to run oxlint/oxfmt instead of
  eslint/prettier
- Update .vscode/extensions.json (oxc replaces eslint/prettier/vitest) and
  settings.json (oxc becomes the default formatter for TS/JS)
- Add 'oxlint', 'oxfmt', 'oxc', 'nodenext' to cspell dictionary
- Rewrite README 'Development' section to describe the new toolchain

package-lock.json

@@ -9,6 +9,8 @@
             "version": "0.0.0",
             "license": "MIT",
             "devDependencies": {
+                "@oxfmt/binding-linux-x64-musl": "^0.66.0",
+                "@oxlint/binding-linux-x64-musl": "^1.81.0",
                 "@types/node": "^22.10.0",
                 "c8": "^10.1.3",
                 "check-outdated": "^2.13.0",
@@ -906,7 +908,6 @@
                 "x64"
             ],
             "dev": true,
-            "optional": true,
             "os": [
                 "linux"
             ],
@@ -1210,7 +1211,6 @@
                 "x64"
             ],
             "dev": true,
-            "optional": true,
             "os": [
                 "linux"
             ],