Support Bun frontend `process.env` prefixing (e.g. `BUN_PUBLIC_*`)

[yamcodes]

When using arkenv in a Bun + React project, process.env is not defined in the frontend runtime. Bun only exposes environment variables that are explicitly prefixed (default: BUN_PUBLIC_*) and accessing process.env directly throws a runtime error.

Additionally, during the build step, Bun's bundler defaults to browser builds, which causes import errors such as:

import { styleText } from "util";
             ^
error: Browser polyfill for module "node:util" doesn't have a matching export named "styleText"

Steps to Reproduce:

1. Create a clean React template with bun init.
2. Install arkenv.
3. Import and call createEnv.
4. Run bun serve → runtime error: process is not defined.
5. Run bun build → bundler error on styleText.

Expected behavior:

arkenv should support Bun's process.env model, allowing retrieval of all variables with a given prefix (e.g., BUN_PUBLIC_*).

Workaround:

Manually construct the env object and pass only the prefixed vars to the schema:

import { type } from "arktype"

const envType = type({ MY_VAR: "string" })
const env = envType.assert({ MY_VAR: process.env.BUN_PUBLIC_MY_VAR })
export default env

Related:

• Bun issue: ENV variables in a frontend dev server oven-sh/bun#19313
• Support runtime access in Vite for prefixed vars (e.g. VITE_*) #288 (Vite frontend import.meta.env prefixing)

Action Items:

• Add support for collecting env vars by a configurable prefix (default: BUN_PUBLIC_*).
• Ensure builds targeting browser/bun don't attempt to import Node-only utilities like util.styleText.

[yamcodes]

Note that this could also be relevant for Vite and Next.js