fix(cron): reject invalid cron expressions on disabled jobs before persisting

[suboss87]

Closes openclaw#74459

Problem

openclaw cron edit <id> --cron "invalid expr" on a disabled job silently persisted the invalid expression. Two bugs:

1. ops.update only calls computeJobNextRunAtMs (which validates via croner) for enabled jobs. Disabled jobs skip that path entirely, so invalid cron syntax passes through to persist().
2. When the user later ran cron edit --enable, applyJobPatch set job.enabled = true before computeJobNextRunAtMs threw, leaving the in-memory state.store.jobs entry with enabled: true even though persist was never reached. This "live state" corruption persisted until the next forced reload from disk.

Root cause

src/cron/service/ops.ts:update:

applyJobPatch(job, patch, ...); // mutates job.enabled = true in-place
// ...
if (job.enabled) {
  job.state.nextRunAtMs = computeJobNextRunAtMs(job, now); // only here does croner throw
}
// For disabled jobs: skips computeJobNextRunAtMs entirely → persist runs with invalid expr

Fix

Added validateCronScheduleExpr(schedule) to src/cron/validate-timestamp.ts. It dry-runs computeNextRunAtMs in a try/catch to detect croner parse errors for any cron-kind schedule.

Three call sites:

• gateway/server-methods/cron.ts — cron.add and cron.update handlers: validate before reaching context.cron.* (returns structured error to caller)
• src/cron/service/ops.ts — update: validate before applyJobPatch so the job object is never mutated when the expression is invalid (defense in depth)

Tests

New file src/cron/service.cron-invalid-expr.test.ts (3 tests):

• Rejects invalid cron expression on a disabled job; original schedule unchanged
• Rejects invalid expression when trying to enable with the bad schedule
• Accepts a valid cron expression change on a disabled job

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Generated by Claude Code

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[devin-ai-integration]

✅ Devin Review: No Issues Found

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