feat: add IO.read method with prompt and stdin input buffer

Implement a new static `IO.read(prompt)` method in the IO class that writes a prompt string to stdout and reads a line from stdin into a fixed 1024-byte buffer. The C implementation adds a `MAX_READ_LEN` constant, an `ioRead` function using `fgets`, and registers the method via `wrenDefineStaticMethod`. The builtin source string is updated to include the new Wren method definition.

builtin/io.wren

@@ -79,6 +79,11 @@ class IO {
     return obj
   }
 
+  static read(prompt) {
+    IO.write(prompt)
+    return IO.read
+  }
+
   static writeObject_(obj) {
     var string = obj.toString
     if (string is String) {