JoaoMarcos44 (inline cli.py:64): the ENFORCEMENT="off" and "no measured files
changed" branches returned before the --json formatter, so
`python -m scripts.code_health --base HEAD --head HEAD --json` succeeded with prose
on stdout and json.loads() raised.
Both early successes now print the empty findings list `[]` on stdout and move
the human explanation to stderr; findings and zero-finding measured diffs were
already JSON. Exit codes are unchanged on all four paths.
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