docs(drill): env2 seeded data-path soak - site-x and central failovers with live data and S&F, no buffered loss (#116)

Unreplicated, the site-x survivor came up empty (by design: no LocalDb peer);
replicated, kill and freeze each lost only the 26-30 s takeover window, every
buffered message was delivered once, and the 4 duplicate ticks came from the
frozen victim's 6 s zombie window. Central kill: 0 gap.

Claude-Session: https://claude.ai/code/session_01GT67ACmpMR7b9LGRPLijMi

docker-env2/README.md

@@ -77,8 +77,16 @@ bash docker-env2/deploy.sh
 
 # 3. Seed env2's single test site (first-time only)
 bash docker-env2/seed-sites.sh
+
+# 4. Optional: live data + store-and-forward load for site-x (opc-plc, a read-only
+#    Galaxy attribute, and the scadabridge-env2-sfsink HTTP sink) — the #116 soak load
+bash docker-env2/seed-data-path.sh
 ```
 
+Site-x's LocalDb is **replicated** (node-a dials node-b on 8083, same dev key on both),
+like the rig's site-a. Without it a site failover brings up an active node with no
+deployed instances, connections or S&F buffer.
+
 The seed also creates a **native alarm source demo**: a `MxAlarmDemo` template with a
 `GalaxyAlarms` native alarm source bound to the shared MxGateway connection, plus a
 deployed `MxAlarmDemo-1` instance on site-x. This exercises the read-only native alarm