When hive-c0re can't read resource-limits.json and a limits drop-in
already exists, it keeps the drop-in, but it wrote no memory cap file. A
container whose runtime dir had no file yet (hive-c0re upgraded, /run
not cleared) then started with no heap ceiling and no subagent
MemoryHigh=, silently. `stage_limits` now writes the file on every
call: from the new limits, or from the last `MemoryMax=` in the kept
drop-in (`infinity` when it has none or can't be read).
A missing or malformed cap file at boot is no longer silent. The
generators run before the container's journal and an nspawn container
has no /dev/kmsg, so a oneshot `hyperhive-memory-cap-check.service`
logs a warning naming the path. The agent then runs with no JSC heap
ceiling and no subagent MemoryHigh=; the container's MemoryMax= still
applies.
module-eval-agent-memory gains a case pinning how the ceiling reaches
claude: `hive-agent` and `hive-subagent-daemon` neither set nor unset
BUN_JSC_forceRAMSize, both generators and the check unit are installed.
Part of #5081 (slice S0-2).
An agent's memory cap was rendered into its flake (`memoryMaxBytes` →
`services.hyperhive.agent.claudeMemoryMaxBytes`), so the closure depended
on it and a changed cap reached the JSC heap ceiling and the subagent
`MemoryHigh=` only after a rebuild.
hive-c0re now writes the effective `MemoryMax=` in bytes to the agent's
runtime dir (`/run/hive/memory-max-bytes` inside) in `write_dropins`,
from the same value the drop-in gets. The file is removed for
`infinity` or a RAM percentage, and left alone when the drop-in is kept.
Inside the container, `nix/agent-modules/memory-cap.nix` reads it at
boot: an environment generator sets `BUN_JSC_forceRAMSize` (75%) for
every unit and `machinectl shell`, `/etc/set-environment` exports it in
login shells, and a unit generator writes `MemoryHigh=` (2/3) as a
drop-in for `hive-subagent-daemon`.
The render drops `memoryMaxBytes`, the agent option is removed (both
spellings fail eval with a removal message), and
`effective_memory_bytes_from` goes with its only caller.
Part of #5081 (slice S0-2).
