fix(ci): retry on disk-space errors in check-dagger

Dagger engine occasionally runs out of disk during `flutter pub get`
when multiple CI jobs run in parallel.  Space typically frees up within
~60 seconds as other containers finish.  Add "No space left on device"
as a retryable condition with a 60 s back-off so PR runs survive the
transient shortage (run 4199480 was the trigger).

Taskfile.yml

@@ -286,6 +286,9 @@ tasks:
             RC=$?
             if [ "$attempt" -lt 3 ] && grep -qE "connection reset|context canceled|connection refused" "$DAGGER_OUT"; then
               echo "$(_ts) dagger: network error on attempt $attempt/3, retrying..." >&2
+            elif [ "$attempt" -lt 3 ] && grep -q "No space left on device" "$DAGGER_OUT"; then
+              echo "$(_ts) dagger: disk space error on attempt $attempt/3, waiting 60s for space to free up..." >&2
+              sleep 60
             else
               return "$RC"
             fi