Blueprint accepting OS-level environment variable

This blueprint:

{
  "login": true,
  "steps": [
    {
      "step": "runPHP",
      "code": "<?php require_once 'wordpress/wp-load.php'; wp_insert_post( [ 'post_title' => 'env', 'post_content' => print_r( $_ENV, true ) ] );"
    }
  ]
}

Generates a post with this content:

Array
(
  [USER] => web_user
  [LOGNAME] => web_user
  [PATH] => /
  [PWD] => /
  [HOME] => /home/web_user
  [LANG] => C.UTF-8
  [_] => cli.ts
  [USE_ZEND_ALLOC] => 0
)

It can be a useful addition for blueprints started using the CLI in this way:

TEST="test" bun cli.ts server --blueprint=./test.json

To inherit the TEST environment var. This is a quite advanced option so it should be available only to PHPRunOptions. The env record should be open to be overwritten by the caller. Such as:

```json
{
  "login": true,
  "steps": [
    {
      "step": "runPHPWithOptions",
      "options": {
        "env": {
          "TEST": "false"
        },
        "code": "<?php require_once 'wordpress/wp-load.php'; wp_insert_post( [ 'post_title' => 'env', 'post_content' => print_r( $_ENV, true ) ] );"
      }
    }
  ]
}

So that it will be possible to write this for rapid prototyping:

TEST="true" bun cli.ts server --blueprint=./test.json

The CLI should have a list of env vars to exclude, such as other security measures.

Addendum: Apparently, $_ENV does not have the values passed if used in the code entry. This may be a bug.

Start with cli.ts and the runPHPWithOptions/PHPRunOptions entry points, then inspect how the blueprint's PHP code receives environment variables. Verify that inherited variables such as TEST are available, caller-provided env values override them, and excluded variables remain unavailable; also investigate the addendum about $_ENV not receiving values in code entries.