fix(cron): skip validation for disabled cronjobs

[chaodu-agent]

What problem does this solve?

validate_cronjobs() validates all cronjob configs at startup, including those with enabled: false. This means a disabled job with an invalid cron expression or timezone causes openab to fail at startup, even though the job would never be scheduled.

This contradicts the user expectation that enabled: false means "this job does not affect the system."

The runtime scheduler (parse_job_list()) already correctly skips disabled jobs — only the startup preflight validation was inconsistent.

Discovered by 擺渡法師 (Codex) during four-monk review of PR #638.

Changes

File	What
src/cron.rs	Add if !job.enabled { continue; } to validate_cronjobs()
src/cron.rs	Add 2 tests: disabled job with invalid cron passes, enabled job with invalid cron still fails

Testing

running 7 tests
test cron::tests::validate_cronjobs_enabled_with_invalid_cron_still_fails ... ok
test cron::tests::validate_cronjobs_invalid_timezone_fails ... ok
test cron::tests::validate_cronjobs_disabled_with_invalid_cron_passes ... ok
test cron::tests::validate_cronjobs_unknown_platform_fails ... ok
test cron::tests::validate_cronjobs_valid_passes ... ok
test cron::tests::validate_cronjobs_unconfigured_platform_fails ... ok
test cron::tests::validate_cronjobs_invalid_cron_fails ... ok

test result: ok. 7 passed; 0 failed; 0 ignored; 0 measured; 170 filtered out

Related

• Follow-up to PR fix(chart): align cronjob config with openab binary + add usercron support #638 and PR fix(chart): use hasKey for boolean enabled to avoid Go template default trap #639
• Aligns startup validation with runtime scheduling semantics

[github-actions]

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