feat: emulate rust's process api more closely

Yoink some docs as well

src/Stdio.php

@@ -6,6 +6,10 @@ namespace Nih\CommandBuilder;
 
 use Stringable;
 
+/**
+ * Describes what to do with a standard I/O stream for a child process when
+ * passed to the stdin, stdout, and stderr methods of {@see Command}.
+ */
 final class Stdio
 {
     public const INHERIT = 0;
@@ -25,27 +29,44 @@ final class Stdio
     ) {
     }
 
+    /**
+     * The child inherits from the corresponding parent descriptor.
+     */
     public static function inherit(): self
     {
         return new self(self::INHERIT, null);
     }
 
+    /**
+     * A new pipe should be arranged to connect the parent and child processes.
+     */
     public static function piped(): self
     {
         return new self(self::PIPE, ['pipe', 'r']);
     }
 
+    /**
+     * This stream will be ignored. This is the equivalent of attaching the
+     * stream to `/dev/null`.
+     */
     public static function null(): self
     {
         return self::file('/dev/null', 'a+');
     }
 
+    /**
+     * Like piped, but instead of capturing the stream into a handle, read
+     * and/or write from/to a file.
+     */
     public static function file(string|Stringable $file, string $mode): self
     {
         return new self(self::FILE, ['file', (string) $file, $mode]);
     }
 
     /**
+     * Like piped, but instead of capturing the stream into a handle, read
+     * and/or write from/to a stream.
+     *
      * @param resource|StreamReadable|StreamWritable $stream
      */
     public static function stream($stream): self