- `concat` was used in the clara.rules.memory/add-insertions! function in a way that caused the lazy seq to stack many nested lazy seq's "in front" of the first element of the final seq.  When these insertions needed to be retracted, this first element of the lazy seq needs to be realized.  To realize it costs stack frames for every level of nesting that was done.  Doing somewhere above ~4K insertions will reveal a stackoverflow under typical JVM max stack frames settings.
- Exposed this issue in a test and fixed it.