[codex-cli] Add ripgrep as a dependency for node environment (#2237)

## Summary
Ripgrep is our preferred tool for file search. When users install via
`brew install codex`, it's automatically installed as a dependency. We
want to ensure that users running via an npm install also have this
tool! Microsoft has already solved this problem for VS Code - let's not
reinvent the wheel.

This approach of appending to the PATH directly might be a bit
heavy-handed, but feels reasonably robust to a variety of environment
concerns. Open to thoughts on better approaches here!

## Testing
- [x] confirmed this import approach works with `node -e "const { rgPath
} = require('@vscode/ripgrep'); require('child_process').spawn(rgPath,
['--version'], { stdio: 'inherit' })"`
- [x] Ran codex.js locally with `rg` uninstalled, asked it to run `which
rg`. Output below:

```
⚡ Ran command which rg; echo $?
  ⎿ /Users/dylan.hurd/code/dh--npm-rg/node_modules/@vscode/ripgrep/bin/rg
    0

codex
Re-running to confirm the path and exit code.

- Path: `/Users/dylan.hurd/code/dh--npm-rg/node_modules/@vscode/ripgrep/bin/rg`
- Exit code: `0`
```

package.json

@@ -3,8 +3,8 @@
   "private": true,
   "description": "Tools for repo-wide maintenance.",
   "scripts": {
-    "format": "prettier --check *.json *.md .github/workflows/*.yml",
-    "format:fix": "prettier --write *.json *.md .github/workflows/*.yml"
+    "format": "prettier --check *.json *.md .github/workflows/*.yml **/*.js",
+    "format:fix": "prettier --write *.json *.md .github/workflows/*.yml **/*.js"
   },
   "devDependencies": {
     "prettier": "^3.5.3"