Tell harness external protocol

<?php
require 'examples/boot.php';

$controller = __DIR__.'/controller.sh';
$command = [
    'bash',
    $controller,
    'Inspect this project and report one actionable risk.',
];
$process = proc_open(
    $command,
    [0 => ['pipe', 'r'], 1 => ['pipe', 'w'], 2 => ['pipe', 'w']],
    $pipes,
    dirname(__DIR__, 3),
);
if (! is_resource($process)) {
    throw new RuntimeException('Unable to start the Tell shell controller.');
}

fclose($pipes[0]);
while (($line = fgets($pipes[1])) !== false) {
    $frame = json_decode($line, true, flags: JSON_THROW_ON_ERROR);
    echo $frame['sequence'].' '.$frame['type']."\n";
}
$errors = stream_get_contents($pipes[2]);
fclose($pipes[1]);
fclose($pipes[2]);
$exit = proc_close($process);

if ($errors !== '') {
    fwrite(STDERR, $errors);
}
if ($exit !== 0) {
    throw new RuntimeException("Tell agent protocol exited with {$exit}.");
}