aeon.yml: `self-improve` cron `0 18 1/2 * *` may be invalid in GitHub Actions cron parser

Opus finding

aeon.yml: `self-improve` cron `0 18 1/2 * *` may be invalid in GitHub Actions cron parser

• aeon.yml:131

GitHub Actions uses POSIX cron via the croner/cron parsers and accepts step expressions, but the day-of-month step `1/2` (every other day starting on the 1st) is not portable — Vixie cron accepts it; GitHub Actions' parser (croner) historically rejects step values on DOM without `*` and the comment 'every other day' is also misleading because `1/2` resets at month boundaries (e.g. day 31 then day 1 is a one-day gap; day 30 to day 1 in a 31-day month is a two-day gap from the 29th). The schedule is also disabled (enabled: false), so impact is dormant, but if the operator flips it on, the cron will either fail validation or fire on an irregular cadence inconsistent with the 'every other day' comment.