* fix(cron): add default retention to per-run job output to bound disk usage (#52383)
Per-run cron output (cron/output/<job>/<timestamp>.md) is written once
per execution and was never pruned, so a frequently-scheduled job on
a long-running deploy accumulates one file per run indefinitely and
can fill the volume ('no space left on device').
save_job_output() now keeps the most recent N output files per job and
removes older ones. N defaults to 50 and is configurable via
cron.output_retention; a non-positive value disables pruning for
operators who manage cleanup externally.
Salvaged from #52402 by @0xDevNinja.
Closes#52383
* fix(config): add cron.output_retention to DEFAULT_CONFIG
Follow-up to #52383: the retention config key was functional via
get()-with-default but missing from DEFAULT_CONFIG, so the deep-merge
wouldn't auto-populate it for new installs. Add it explicitly.
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Co-authored-by: 0xDevNinja <manmit0x@gmail.com>
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