docs: record Matter/IPv6 findings — stale matter-server mDNS address, SSID cleanup, ER-X ULA infeasibility (W1N-207)

docs/lan-overview.md

@@ -13,6 +13,11 @@ from each section below.
 > **Verified live on 2026-08-06** by read-only SSH from the WSL client. No
 > changes were made. `gfw.windy.lan` root SSH was re-verified the same day after
 > the key was installed; its facts below are from the fresh probe.
+>
+> **IPv6 re-verified 2026-08-20** (read-only): UniFi controller `Default`
+> network IPv6 enabled (SLAAC/RA), both APs hold global SLAAC addresses, and
+> `zhiqiangf` key-only AP SSH re-confirmed. See
+> [unifi-network.md](unifi-network.md).
 
 ---
 
@@ -76,7 +81,10 @@ from each section below.
 | Port-forwards | `hass`→192.168.55.11:8123 · `transmission`→192.168.66.51:51413 · `ssh`→192.168.66.36:22 (orig 5822) · `openvpn`→192.168.66.32:1194 · WAN iface pppoe0 |
 | Management | SSH TCP 22 · EdgeOS GUI HTTP 80 / HTTPS 443 |
 
-**Static DHCP mappings (LAN66):** `OnePlus-12`=.37, `gfw`=.1, `hp-nas`=.32, `pihole`=.36, `pve`=.26, `transmission`=.51, `ubnt-6`=.6, `ubnt-app`=.46, `windy-pc`=.99. LAN55: `Aqara-Hub-M3-10CB`=.248.
+**Static DHCP mappings (LAN66):** `OnePlus-12`=.37, `gfw`=.1, `hp-nas`=.32, `pihole`=.36, `pve`=.26, `transmission`=.51, `ubnt-6`=.6, `ubnt-app`=.46, `windy-pc`=.99. LAN55: `Aqara-Hub-M3-10CB`=.248, `SmartThings-Station`=.48, `espressif`=.47,
+`hass`=.11, `hass-wifi`=.250, `ihost`=.12, `midea_ac_0418`=.10,
+`midea_e3_0198`=.42, `roborock-wm-a141`=.43, `samsung-hub`=.251,
+`matter`=.41 (added 2026-08-20).
 
 > **Note:** `LAN_IN`/`LAN_OUT` are defined but not applied to an interface, so LAN55
 > and LAN66 are bidirectionally reachable by default. Do not rely on those rules as
@@ -168,6 +176,35 @@ See [docs/unifi-openclash-localhost.md](../docs/unifi-openclash-localhost.md).
 Both reported **Connected** to `http://192.168.66.46:9080/inform` on 2026-08-06.
 AP SSH account is `zhiqiangf` (key-only, verified). See [docs/unifi-network.md](../docs/unifi-network.md).
 
+**IPv6 (verified 2026-08-20):** both APs hold global SLAAC IPv6 addresses on
+`br0` — U6 Lite `240e:3bd:235:1fb1::/64` (LAN66), UAP-AC-Lite
+`240e:3bd:235:1fb2::/64` (LAN55) — with RA default routes via `gw`; the
+controller's `Default` network has IPv6 enabled (SLAAC). Prefixes are dynamic
+(PPPoE PD), so they rotate on redial. Details:
+[docs/unifi-network.md](../docs/unifi-network.md).
+
+**SSID cleanup (2026-08-21, W1N-207):** the SmartThings Element/vWire provisioning
+SSIDs (`element-8a0d5133c9438f12`, `vwire-8b2d67469e455785`, `vport-F09FC22004E9`)
+were removed/disabled in the controller (`element_adopt` setting off, element wlanconf
+deleted, connectivity `x_mesh_essid`/`x_mesh_psk` cleared, device `x_vwirekey` removed,
+`vwire_enabled`/`mesh_sta_vap_enabled=false`) and cleared from both APs; all
+vwire/vport/element flags on the remaining SSIDs are now `disabled`.
+
+**Stable ULA on gw: not feasible (2026-08-21, W1N-207):** EdgeOS v3.0.1
+`interfaces switch switch0` rejects a static `ipv6 address`, and an explicit
+`router-advert` node *replaces* the DHCPv6-PD-slaac RA (drops the delegated GUA
+prefix from radvd → LAN55 loses IPv6 egress after RA expiry). Attempted and rolled
+back cleanly (no `save`; gw config unchanged). Consequence: after a PD rotation,
+restart HA's matter-server (see [hosts/hass.windy.lan.md](../hosts/hass.windy.lan.md))
+to clear stale IPv6 mDNS caches.
+
+**LAN55 RA environment (observed 2026-08-21):** besides `gw`, the SmartThings
+Station (.48) and Aqara M3 (.248) act as Thread border routers and advertise ULA
+prefixes (`fd00:5a7:6415:1::/64`, `fd97:d580:16fe:1::/64`); several LAN55 hosts
+(HA, PVE, UAP-AC-Lite) have IPv6 forwarding enabled and mark themselves as
+routers in NDP. This is normal Thread-BDR behaviour and was not the Matter
+failure cause.
+
 ---
 
 ## Quick orientation (who runs what)