📝 Update README & specifications.

README.md

@@ -44,6 +44,14 @@ a virtual node whose I/O behavior is driven by scripted scenarios.
   config, 255 = DHCP), WBM-equivalent pages (Port/Ethernet, Modbus
   settings, Modbus Mapping, I/O Config), and device-state persistence
   with factory reset.
+- **Host network settings** *(requested, planned — spec §15)*: a
+  Docker-gated, opt-in settings page (`WAGO_SIM_HOSTNET=1` **and**
+  container detection) that lists the host OS's network interfaces
+  and adds/removes/changes their IPv4 addresses through a
+  whitelisted host-side agent — so simulated node re-addressing
+  (DIP dedicated-IP mode) and network-loss fault cases become real
+  on the bench network. Runtime-only changes, snapshot/undo, and an
+  audit log; fully absent (404) when the flag is off.
 - **Long-duration (continuous) simulation** *(requested, planned — see
   `docs/spec/software-spec.md` §8)*: endurance/soak testing over days or
   weeks of simulated time. Designated inputs are driven from streaming
@@ -343,6 +351,34 @@ requirement ID for each item in parentheses.
       protocol tracing, diagnostics and fault injection (FR-14.2.5–
       14.2.6); scoping questions to answer before planning (§14.3).
 
+### Requested — host network settings (spec §15, not yet scheduled)
+
+- [ ] Host OS IP settings page (FR-15.2.1–15.2.3): exposed in the web
+      UI only when `WAGO_SIM_HOSTNET=1` **and** running inside Docker
+      (compose sets `WAGO_SIM_IN_DOCKER=1`; `/.dockerenv` as a
+      supplementary signal); authenticated page listing the host's
+      interfaces with link state and current IPv4 addresses, read
+      from live host state, with add/remove/change-address operations
+      validated client- and agent-side; routes answer 404 when
+      disabled — no dormant surface.
+- [ ] Host-side agent + safety rails (FR-15.2.4–15.2.8): a
+      whitelisted companion service on the host (Unix socket mounted
+      into the container; `pyroute2`/`ip` on Linux v1, systemd unit in
+      `deploy/`) — interface whitelist, runtime-only (non-persistent)
+      address changes so a host reboot restores deployed addressing,
+      snapshot before every mutation with undo/restore, single-line
+      audit log; degraded state (agent unreachable) shows a banner
+      and answers 503 without affecting the rest of the UI; readonly
+      mode hides the page and 403s mutations.
+- [ ] DIP dedicated-IP integration (FR-15.2.9): applying a DIP-switch
+      address change in dedicated-IP mode routes through the agent so
+      the derived IP lands on the host NIC — the PLC on the bench
+      network must genuinely re-connect to the new node address, like
+      a physical coupler after a DIP change (ties into §11
+      FR-11.3.3); scoping questions (platform scope, bridge vs host
+      networking, agent auth, IPv6, link up/down) in §15.4 before
+      planning.
+
 ### Web UI (spec §10) — in implementation
 
 - [x] Spec §10.3–10.6 updated with binding implementation decisions: