fix: don't advance lastDate() for ticks skipped by waitForCompletion

[chatman-media]

Description

When waitForCompletion is enabled and a callback is still running, the scheduled tick is skipped early in fireOnTick():

async fireOnTick() {
  // skip job if previous callback is still running
  if (this.waitForCompletion && this._isCallbackRunning) return;
  ...
}

However, this.lastExecution = new Date() was assigned at the call sites before invoking fireOnTick() (the normal timer path, plus the runOnInit and threshold-"execute immediately" paths). As a result lastExecution advanced on every tick check, even when the callback was skipped because the previous one was still running.

This means lastDate() / lastExecution reported the moment of the last tick check rather than the last real execution, which contradicts their documented meaning (lastDate: Provides the last execution date.) and is inconsistent with nextDate()/nextDates() which describe when an onTick actually activates.

Related Issue

Closes #1048

Motivation and Context

The fix moves the lastExecution assignment into fireOnTick(), placed right after the already-running guard, so it is only updated when a callback truly fires. The four call-site assignments are removed (the runOnInit, normal-tick, and threshold paths all call fireOnTick() immediately after, so firing behaviour is unchanged; the skipped path no longer advances the timestamp).

This keeps the existing documented semantics intact — confirmed by the pre-existing tests "should give the correct last execution date" and the #710 regression test, both of which still pass.

How Has This Been Tested?

Added a regression test under the waitForCompletion and job status tracking suite. With a 1.5s callback on a * * * * * * schedule and waitForCompletion: true:

• t=1000ms: callback Accessing CronTime #1 starts → lastDate() is 1000
• t=2000ms: tick is skipped (callback Accessing CronTime #1 still running) → lastDate() must still be 1000 (was 2000 before this fix)
• t=3000ms: callback Bug with december #2 starts → lastDate() is 3000

The test fails on main (Expected: 1000, Received: 2000) and passes with the fix. Full suite: 162 passed. ESLint + Prettier clean, tsc build clean. Ran with TZ='Europe/Paris' as configured.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.
• If my change introduces a breaking change, I have added a ! after the type/scope in the title (n/a — not a breaking change).