WorkflowStub skips due SQLite tasks during their exact due second #1026

Defect

WorkflowStub::runReadyTasks() can leave an already-due SQLite task untouched during its exact due second. This makes fake workflow tests depend on elapsed wall time and can leave a test at an earlier phase before an explicit clock advance.

WorkflowTask persists available_at using Y-m-d H:i:s.u. The helper passes now() as a DateTime query binding; Laravel serializes that binding to whole seconds. SQLite compares these timestamp strings lexically, so even 2026-01-02 00:00:01.000000 is greater than 2026-01-02 00:00:01.

This is the same precision mismatch previously corrected for schedule ticking in #505, in a separate helper predicate. #505's delivered schedule acceptance remains valid. The unfixed helper predicate is in src/V2/WorkflowStub.php::runReadyTasks() and is also present in the 2.20.2 source.

Reproduction

Confirmed with installed published Workflow 2.6.2 and 2.17.1, PHP 8.4.27, Laravel 13 and an in-memory SQLite database. Run in a migrated Laravel test using RefreshDatabase:

use Illuminate\Support\Carbon;
use Workflow\V2\Workflow;
use Workflow\V2\WorkflowStub;
use function Workflow\V2\timer;

class WaitOneSecond extends Workflow
{
    public function handle(): string
    {
        timer(1);
        return 'done';
    }
}

$this->travelTo(Carbon::parse('2026-01-02 00:00:00.500000', 'UTC'));
WorkflowStub::fake();
WorkflowStub::make(WaitOneSecond::class, 'clock-precision')->start();
$this->travel(1)->seconds();
$processed = WorkflowStub::runReadyTasks();
$this->assertTrue(WorkflowStub::load('clock-precision')->completed());

Expected: the timer is due and the workflow completes. Actual on both versions:

now=2026-01-02 00:00:01.500000
available_at=2026-01-02 00:00:01.500000
SQL binding=2026-01-02 00:00:01
processed=0 completed=false

The exact whole-second case (.000000) fails identically. Advancing one additional second lets both cases complete, without changing the workflow. The four exact-deadline cases fail deterministically across the two versions; all four later-clock controls complete. The 2.20.2 artifact has not been run in this reproduction.

Observed scope: the synchronous fake helper on SQLite. No production-worker failure or data loss was established.

Acceptance

• Preserve the task model's persisted precision in the helper's due predicate, without changing global Laravel DateTime serialization.
• Cover whole-second equality, fractional equality, an elapsed deadline within the same second, and a future fractional task that must remain pending.
• Preserve the helper's task limit, ordering, configured task models and no-progress guard.
• Verify the affected SQLite behavior and supported MySQL/PostgreSQL query behavior, then qualify the published correction with this reproduction.
• Reuse the existing timestamp conventions; no polling workaround, new scheduler or protocol change is needed.