navi: overlay the hive config onto the instance's own ...

An instance that knows a hive with the swarm key starts from the hive
document: layers that apply to it are merged over its local config, fields
the hive does not mention stay local, and an empty answer means 'run exactly
your own config'. Settings, profiles, LLM routes and MCP servers are covered;
database URL, ports, auth switches and the channel's own settings can never be
overridden.

Startup fetches with a short timeout, falls back to the last validated overlay
on disk and refuses to crash-loop on a document that killed the previous start.
A live refresh applies secrets and timeouts in place (the frozen singleton is
written through one deliberate escape hatch), rebuilds profiles from their
local base and reports everything else as restart_required. The hive reaches
the instance by push, by the announce reply and by a retry sweep; every apply
is acked back, which is what the hive's status view reads.

swarm stage 2: peer-to-peer channel — /peer endpoints + peer tool ...

Server side (navi/api/routes/peer.py, port 8099):
- GET /peer/hello — open discovery ping (name, uuid prefix, version)
- GET /peer/status — PSK; identity, uptime, machine facts, hive view
- POST /peer/ask — PSK; one-shot agent run under PEER_ASK_PROFILE
  (default server_admin) answers, one concurrent ask at a time
- loop guard: answering agent runs without the peer tool (deterministic
  recursion cut) + own-uuid asks refused with 409
- verify_swarm_key in navi/swarm.py accepts .swarm-key.previous
  (rotation window, constant-time)

Client side (navi/tools/peer.py):
- peer tool: list (hive book, stale cache fallback marked), status,
  ask by swarm name; asks go direct peer-to-peer, hive never on the
  message path
- audit events on both sides (peer.ask_sent/received/answered/failed)

peer tool added to server_admin, navi_code, developer profiles.

swarm stage 1: instance identity, PSK, hive registry, announce loop ...

- navi/identity.py: adjective-animal names + uuid in instance.json
  (generated at install, renameable by hand)
- navi/swarm.py: HiveAnnouncer - periodic POST /announce to the hive
  with non-blocking reachability tracking (transitional logs, /health
  export, hive_status context provider reports outages to the agent)
- hive/: standalone FastAPI address book (SQLite, port 8087, PSK via
  X-Swarm-Key with .swarm-key.previous rotation window, TTL online
  status, host from client IP, port from payload). Not installed or
  started by default - run manually on the main server.
- ports moved to 8099 (API) / 8098 (UI MCP)
- install.sh: PYTHONIOENCODING=utf-8 in the systemd unit, generates
  instance.json and .swarm-key on fresh installs