The startup banner moves from stdout to stderr, so a `completion`
script, a `config get` value and the hidden `__complete` command print
only their own output. `--quiet`, `--cron` and `--json` still suppress
it.
A failing `remote info`, `prune` or `snapshot remove` under `--json`
now reports its error on stderr. Their reporters returned early under
`--json`, so the failure reached neither stream.
`snapshot verify --quiet` writes no report. A failure is still
returned and printed on stderr, with the same exit status.
Judgement call: the banner's stream, posted on the issue for the owner.
Model: opus-5-5
