fix: ensure a newline is inserted before delimiter

[builtinnya]

This PR addresses two issues with the existing output redirect functionality:

1. In the current implementation, if the kubectl output (kubectl $*) does not end with a newline, the action fails. This is because the delimiter (EOF) is inserted on the same line as the output. This PR ensures that a newline is always added before the end delimiter to prevent this issue.

2. The current multiline delimiter is a literal EOF, which does not adhere to the recommendations in the official documentation. This PR replaces the literal EOF with a randomly generated delimiter, following the example provided in the official documentation.