[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`
```

codex-cli/bin/codex.js

@@ -43,7 +43,7 @@ switch (platform) {
         targetTriple = "x86_64-pc-windows-msvc.exe";
         break;
       case "arm64":
-        // We do not build this today, fall through...
+      // We do not build this today, fall through...
       default:
         break;
     }
@@ -65,9 +65,43 @@ const binaryPath = path.join(__dirname, "..", "bin", `codex-${targetTriple}`);
 // receives a fatal signal, both processes exit in a predictable manner.
 const { spawn } = await import("child_process");
 
+async function tryImport(moduleName) {
+  try {
+    // eslint-disable-next-line node/no-unsupported-features/es-syntax
+    return await import(moduleName);
+  } catch (err) {
+    return null;
+  }
+}
+
+async function resolveRgDir() {
+  const ripgrep = await tryImport("@vscode/ripgrep");
+  if (!ripgrep?.rgPath) {
+    return null;
+  }
+  return path.dirname(ripgrep.rgPath);
+}
+
+function getUpdatedPath(newDirs) {
+  const pathSep = process.platform === "win32" ? ";" : ":";
+  const existingPath = process.env.PATH || "";
+  const updatedPath = [
+    ...newDirs,
+    ...existingPath.split(pathSep).filter(Boolean),
+  ].join(pathSep);
+  return updatedPath;
+}
+
+const additionalDirs = [];
+const rgDir = await resolveRgDir();
+if (rgDir) {
+  additionalDirs.push(rgDir);
+}
+const updatedPath = getUpdatedPath(additionalDirs);
+
 const child = spawn(binaryPath, process.argv.slice(2), {
   stdio: "inherit",
-  env: { ...process.env, CODEX_MANAGED_BY_NPM: "1" },
+  env: { ...process.env, PATH: updatedPath, CODEX_MANAGED_BY_NPM: "1" },
 });
 
 child.on("error", (err) => {
@@ -120,4 +154,3 @@ if (childResult.type === "signal") {
 } else {
   process.exit(childResult.exitCode);
 }
-