mesh-issues: keep the issues bucket at 8 values until the carry can read them, so the bus drops nothing before it is carried (hq ADR 0300 §6)

modules/mesh-issues/README.md

@@ -256,10 +256,12 @@ whole; every other one names the fields given a new value (`set`), the lists add
 a note is kept as itself, not as every note again) and the fields taken away (`unset`). The fold applies them
 as written, so a new kind of operation needs nothing new in the fold.
 
-**The bucket `issues` is the fold of the log**, one value per key, each issue carrying `folded`, the sequence
+**The bucket `issues` is the fold of the log**, each issue carrying `folded`, the sequence
 of its last operation. It is written after the append, at the revision read; one whose write fails after the
 log took the change is behind, and caught up at its next change (the stale append is refused and the log
-folded) or at the next start. Agents and views watch it as before.
+folded) or at the next start. Agents and views watch it as before. It still keeps 8 values per key, so the bus
+cannot drop the older values before the carry has read them; it goes to one value per key (ADR 0300 §3) in a
+follow-up, once the carry has run with a read of those values.
 
 **On start**, the tracker watches its own bucket, carries what the bucket holds and the log does not (below),
 reads the whole log page by page, folds every issue whose last operation is newer than its `folded` — an