mara's ruling: "swarm level overrides replace the hive ui limits. otherwise
dont change the logic."
swarm value present -> it is the value; nothing hive-side is consulted
swarm value absent -> exactly today's chain: per-agent field, else hive
Per field, so a swarm memory ceiling leaves CPU on the hive's chain.
The fallback chain itself is not touched: effective_from_with_swarm calls
effective_from as it was and lets the swarm replace its result, and
effective_with_swarm delegates to effective, so there stays one place the
chain lives. `an_empty_swarm_map_leaves_the_existing_chain_bit_for_bit`
asserts the wrapper is a no-op across every shape the chain distinguishes.
The swarm's caps live in their own swarm-resource-limits.json, not in the
operator's resource-limits.json: different writers, different lifetimes,
and a swarm write into the operator's file would make "reset to hive
defaults" destroy something the operator never set. It is read and written
through the same read_map / write_map, so an unreadable file is an error,
and write_dropins resolves both files through limits_to_apply, whose
keep-the-last-applied-drop-in policy covers the swarm file too.
stage_limits hands limits_to_apply the swarm caps file too, so the
agent's memory-max-bytes copy, which it sizes its heap and subagents
against, is the MemoryMax= systemd enforces: the swarm cap when there is
one.
Nothing writes swarm-resource-limits.json yet; the reader comes with the
swarm's agent-limits bucket later in this series.
37f6a845a0