feat(swarm): unbundle master-only code from agent tarball + sync systemd units on update

Agents now ship with collector/prober/sniffer as systemd services; mutator,
profiler, web, and API stay master-only (profiler rebuilds attacker profiles
against the master DB — no per-host DB exists). Expand _EXCLUDES to drop the
full decnet/web, decnet/mutator, decnet/profiler, and decnet_web trees from
the enrollment bundle.

Updater now calls _heal_path_symlink + _sync_systemd_units after rotation so
fleets pick up new unit files and /usr/local/bin/decnet tracks the shared venv
without a manual reinstall. daemon-reload runs once per update when any unit
changed.

Fix _service_registry matchers to accept systemd-style /usr/local/bin/decnet
cmdlines (psutil returns a list — join to string before substring-checking)
so agent-mode `decnet status` reports collector/prober/sniffer correctly.

.gitignore

@@ -26,3 +26,4 @@ decnet.json
 .coverage
 .hypothesis/
 profiles/*
+tests/test_decnet.db*