docs: expand MVP test guide

Refresh the manual MVP test guide around the current relay, gateway, and
Windows client behavior. The guide now calls out the values to record during a
run, the exact process order, expected gateway lifecycle signals, and a short
gateway restart sanity check.

Also update the README component notes so the control plane and Windows client
docs mention the gateway peer id carried in welcomes.

Test Plan:
- git diff --check
- git diff --cached --check

Refs: MVP manual validation

README.md

@@ -33,7 +33,7 @@ Reliable control-plane schema shared by the QUIC stream handlers:
 
 - endpoint hello messages with role, room, MAC, and datagram budget
 - server welcome mode, reject, peer lifecycle, stats, and disconnect messages
-- initial room gateway-presence status in server welcomes
+- initial room gateway-presence status and gateway peer id in server welcomes
 - room-code, role/MAC, peer-id, and effective-MTU validation
 - length-prefixed JSON control frames for reliable QUIC streams
 
@@ -290,5 +290,5 @@ with direction, peer id, MACs, ethertype/length, frame length, action, and drop
 reason. TAP device read/write errors still stop the bridge.
 Relay lifecycle events are logged as they arrive, including gateway joins and
 peer leaves. The client remembers peer identities from join and catch-up events
-so later leave logs can identify a disconnected LAN gateway or client MAC when
-that peer was known.
+and from the initial welcome, so later leave logs can identify a disconnected
+LAN gateway or client MAC when that peer was known.

TESTING.md

@@ -30,6 +30,15 @@ gateway iface:  eth0
 LAN test host:  <lan-host-ip>
 ```
 
+Keep these values from the logs as you go:
+
+```text
+gateway peer id:
+client peer id:
+client virtual MAC:
+Windows TAP IPv4:
+```
+
 ## Machines
 
 - Relay: public Linux host reachable over UDP.
@@ -37,6 +46,7 @@ LAN test host:  <lan-host-ip>
 - Client: Windows 11 machine with TAP-Windows6 installed.
 
 Use the same room code everywhere, for example `ROOM1`.
+Start order is relay first, gateway second, Windows client last.
 
 ## Build Prerequisites
 
@@ -162,6 +172,7 @@ Expected client output:
 ```text
 prepared TAP adapter ... MAC ... configured and media disconnected before relay connect
 lanparty-client-win connected as peer ...
+relay event: LAN gateway connected as peer ...
 relay route pinned before TAP ...
 relay route verified after TAP activation ...
 TAP driver reports MAC ... and MTU ...
@@ -223,6 +234,34 @@ client. It should appear on the physical port connected to the Linux gateway.
 
 This is the practical MVP acceptance test.
 
+## Lifecycle Sanity Check
+
+Run this after the basic tunnel works. It verifies that the room lifecycle is
+visible to the Windows client and that a gateway restart does not leave stale
+status behind.
+
+1. Stop the gateway with Ctrl-C while the relay and client keep running.
+
+Expected client output:
+
+```text
+relay event: LAN gateway disconnected (peer ..., Normal)
+gateway connected no
+Waiting for LAN gateway
+```
+
+2. Start the gateway again with the same relay, room, cert, and interface.
+
+Expected client output:
+
+```text
+relay event: LAN gateway connected as peer ...
+gateway connected yes
+Connected to LAN gateway
+```
+
+After the reconnect, repeat one quick `ping -S <tap-ip> <lan-host-ip>`.
+
 ## Useful Log Signals
 
 Relay frame forwarding:
@@ -290,6 +329,10 @@ check relay lifecycle logs and duplicate-MAC rejection first.
 If the client says `Waiting for LAN gateway`, check that the gateway uses the
 same room code and is connected to the same relay.
 
+If the client stays on `gateway connected yes` after the gateway has stopped,
+capture the relay and client lifecycle logs. The client should clear this state
+from the gateway peer id it received during welcome or peer-join catch-up.
+
 If the gateway fails with `reports no carrier`, plug the selected Ethernet
 interface into the LAN party switch, bring the interface up, and restart the
 gateway.
@@ -344,3 +387,4 @@ For a useful test report, capture:
 - ping result from `<tap-ip>` to a LAN host
 - switch MAC-table entry for the Windows client MAC
 - LAN game discovery or join result
+- lifecycle sanity-check result