fix(tracker.go): an error reaches the log, the row and the page as a kind, never its text (adversarial review F3, F5)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

internal/progress/tracker.go

@@ -12,6 +12,7 @@ import (
 	"time"
 
 	"git.d-ma.be/mathias/tapir/internal/domain"
+	"git.d-ma.be/mathias/tapir/internal/errkind"
 )
 
 // Planned is one phase of a job, declared up front so the page can show what is coming.
@@ -146,7 +147,7 @@ func (t *Tracker) Fail(key string, err error) {
 		return
 	}
 	t.close(s, domain.StepFailed)
-	t.log.Warn("step failed", "step", key, "elapsed", s.FinishedAt.Sub(s.StartedAt), "err", err)
+	t.log.Warn("step failed", "step", key, "elapsed", s.FinishedAt.Sub(s.StartedAt), "kind", errkind.Of(err))
 	t.save()
 }