Cascading delete ordering

A cache sweep looks like "delete every row nothing points at". It is really a graph traversal, and the order you visit the graph in decides whether it does anything at all.

The shape that works, as one chain:

pin the live record
  → the event log
  → containers whose satellites are keyed on a state flag (and those satellites)
  → containers that cascade to children
  → the remaining containers
  → the leaves, in batches
  → satellite rows already stranded before this run
  → checkpoint + compact
  → unpin