Assert the late-save row is ok to prove the post-save timeout path

The row-saved-late test only checked that one ai_runs row existed, so it
would also pass if the work itself had timed out before the save. It now
requires the row to be ok with no error, which holds only when the work
ended in time and the save alone ran past the deadline.

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

internal/ai/harness/guard_test.go

@@ -316,8 +316,11 @@ func TestRunTimeout(t *testing.T) {
 			t.Fatalf("out = %+v, want no output", out)
 		}
 		assertCalls(t, &f, 1)
-		if rows := runRows(t, cfg.Store); len(rows) != 1 {
-			t.Fatalf("rows = %+v, want one row", rows)
+		// An ok row with no error proves the work ended in time and only
+		// the save ran past the deadline.
+		rows := runRows(t, cfg.Store)
+		if len(rows) != 1 || rows[0].Status != string(StatusOK) || rows[0].Error.Valid {
+			t.Fatalf("rows = %+v, want one ok row with no error", rows)
 		}
 	})
 	t.Run("waiting for a slot", func(t *testing.T) {