The format_output() function returned a string that callers passed to
Rich console.print(), which wraps long lines at terminal width. This
injected literal newline characters into JSON string values (e.g. in
definition_of_done fields), producing invalid JSON that downstream
parsers could not decode (JSONDecodeError: Invalid control character).
For machine-readable formats (json, yaml, plain), format_output() now
writes the rendered output directly to sys.stdout and returns an empty
string. This preserves the exact serialization from json.dumps/
yaml.dump without Rich text processing artifacts.
Refs: #746
Luis Mendes
Jeffrey Phillips Freeman
