app-server spawn strips all environment variables, breaking non-OpenAI model providers #160

Bug

When using a non-OpenAI model provider configured via env_key in ~/.codex/config.toml, invoking codex through the Claude Code plugin fails with:

Missing environment variable: DATABRICKS_TOKEN

Running codex directly from the terminal works fine.

Root Cause

In plugins/codex/scripts/lib/app-server.mjs, SpawnedCodexAppServerClient.initialize() spawns codex app-server with:

this.proc = spawn("codex", ["app-server"], {
  cwd: this.cwd,
  env: this.options.env,  // always undefined — no caller passes env in options
  ...
});

In Node.js, spawn() with env: undefined gives the child process no environment variables at all. The codex app-server subprocess can't see any env vars, so it fails when initializing model providers that require them.

Expected Behavior

The spawned codex app-server process should inherit the parent's environment variables when no explicit env is provided, matching the existing pattern in broker-lifecycle.mjs (line 146) and codex-companion.mjs (line 617).

Steps to Reproduce

1. Configure a non-OpenAI model provider in ~/.codex/config.toml with env_key = "DATABRICKS_TOKEN" (or any custom env var)
2. Export that env var in your shell
3. Invoke the codex plugin from Claude Code
4. Observe the Missing environment variable error

Suggested Fix

- env: this.options.env,
+ env: this.options.env ?? process.env,