Add multiplayer latency test plan

AGRARIAN_DEVELOPMENT_ROADMAP.md

@@ -722,7 +722,9 @@ Target deliverable: A small group can join a server, spawn into one biome, gathe
   pickups, resources, campfires, shelters, wildlife, water sources, weather
   exposure zones, and wildlife spawn managers, with the matching relevancy
   strategy documented for Ground Zero multiplayer tests.
-- [ ] Add basic latency testing.
+- [x] Add basic latency testing. Added an MVP latency test plan with clean LAN,
+  mild WAN, and rough WAN Unreal packet-simulation profiles plus a Windows
+  helper script for the test console commands.
 - [ ] Add disconnect/reconnect handling.
 
 ## 0.1.M Persistence MVP

Docs/MultiplayerNetworkingDesign.md

@@ -245,10 +245,18 @@ MVP target:
 
 - normal gathering/crafting/building should feel acceptable under LAN and
   typical residential broadband latency;
+- clean LAN profile uses 0ms artificial lag and 0% packet loss;
+- mild WAN profile uses 80ms lag, 20ms variance, and 1% packet loss;
+- rough WAN profile uses 160ms lag, 40ms variance, and 3% packet loss;
 - survival stat updates can tolerate low-frequency replication;
 - inventory/crafting feedback should feel responsive enough to test the loop;
 - combat and precision movement prediction are not the first MVP focus.
 
+`Docs/Ops/MultiplayerLatencyTestPlan.md` is the 0.1.L latency gate. It uses
+Unreal packet simulation commands and two packaged clients to check resource
+depletion, item drops, fire/shelter replication, wildlife state, and server
+travel under repeatable profiles.
+
 Initial latency testing should cover:
 
 - join and spawn;

Docs/Ops/MultiplayerLatencyTestPlan.md

@@ -0,0 +1,69 @@
+# Agrarian Multiplayer Latency Test Plan
+
+This is the MVP latency test gate for 0.1.L. It is intentionally small and
+repeatable so the first two-player tests can find obvious replication and
+interaction problems before dedicated-server hosting is stable.
+
+## Scope
+
+Run these tests against the current Ground Zero map:
+
+```text
+/Game/Agrarian/Maps/L_GroundZeroTerrain_Test
+```
+
+The test can use either:
+
+- listen server while dedicated-server packaging is blocked;
+- Linux dedicated server at `play.agrariangame.com:7777` once the gameplay VM is
+  available.
+
+## Network Profiles
+
+Use Unreal packet simulation console variables on the client being tested:
+
+| Profile | Commands |
+| --- | --- |
+| Clean LAN | `Net PktLag=0`, `Net PktLoss=0` |
+| Mild WAN | `Net PktLag=80`, `Net PktLagVariance=20`, `Net PktLoss=1` |
+| Rough WAN | `Net PktLag=160`, `Net PktLagVariance=40`, `Net PktLoss=3` |
+
+Reset after testing:
+
+```text
+Net PktLag=0
+Net PktLagVariance=0
+Net PktLoss=0
+```
+
+## Smoke Steps
+
+For each profile:
+
+1. Start a listen server or dedicated server on the Ground Zero map.
+2. Connect two packaged Windows clients.
+3. Confirm both clients see the same world time and weather.
+4. Gather from a resource node on client A and confirm depletion on client B.
+5. Drop an item on client A and confirm client B sees the pickup only when
+   nearby.
+6. Place or interact with a campfire/shelter and confirm replicated state.
+7. Damage/harvest wildlife if available and confirm state replication.
+8. Trigger `AgrarianServerTravel GroundZero` and confirm clients return to the
+   Ground Zero map.
+9. Record visible hitching, missed interactions, delayed stat updates, or
+   disconnects.
+
+## Pass Criteria
+
+- Both clients remain connected through the clean LAN and mild WAN profiles.
+- Core interactions eventually reconcile under rough WAN conditions.
+- No client can create authoritative inventory, survival, resource, fire,
+  shelter, or wildlife state locally.
+- Any failure is reproducible with the profile, map, client build, server build,
+  and logs recorded.
+
+## Helper Script
+
+`Scripts/LatencyTestProfiles-Windows.bat` prints the console commands for each
+profile and the reset command. It does not automate a full playthrough; the MVP
+gate still requires human observation until gameplay automation matures.

Scripts/LatencyTestProfiles-Windows.bat

@@ -0,0 +1,27 @@
+@echo off
+setlocal
+
+echo Agrarian MVP latency test profiles
+echo.
+echo Clean LAN:
+echo   Net PktLag=0
+echo   Net PktLagVariance=0
+echo   Net PktLoss=0
+echo.
+echo Mild WAN:
+echo   Net PktLag=80
+echo   Net PktLagVariance=20
+echo   Net PktLoss=1
+echo.
+echo Rough WAN:
+echo   Net PktLag=160
+echo   Net PktLagVariance=40
+echo   Net PktLoss=3
+echo.
+echo Reset:
+echo   Net PktLag=0
+echo   Net PktLagVariance=0
+echo   Net PktLoss=0
+echo.
+echo Run these in the client console while connected to the Ground Zero server.
+exit /b 0

Scripts/verify_basic_latency_testing.py

@@ -0,0 +1,73 @@
+#!/usr/bin/env python3
+"""Validate MVP latency testing plan and helper script."""
+
+from pathlib import Path
+import sys
+
+ROOT = Path(__file__).resolve().parents[1]
+
+
+def read(relative_path: str) -> str:
+    path = ROOT / relative_path
+    if not path.exists():
+        raise AssertionError(f"Missing required file: {relative_path}")
+    return path.read_text(encoding="utf-8")
+
+
+def require(content: str, needle: str, context: str) -> None:
+    if needle not in content:
+        raise AssertionError(f"Missing {needle!r} in {context}")
+
+
+def main() -> int:
+    errors: list[str] = []
+    checks = {
+        "Docs/Ops/MultiplayerLatencyTestPlan.md": [
+            "Clean LAN",
+            "Mild WAN",
+            "Rough WAN",
+            "Net PktLag=80",
+            "Net PktLag=160",
+            "Net PktLoss=3",
+            "AgrarianServerTravel GroundZero",
+            "play.agrariangame.com:7777",
+        ],
+        "Scripts/LatencyTestProfiles-Windows.bat": [
+            "Net PktLag=0",
+            "Net PktLagVariance=20",
+            "Net PktLoss=1",
+            "Net PktLagVariance=40",
+            "Net PktLoss=3",
+        ],
+        "Docs/MultiplayerNetworkingDesign.md": [
+            "mild WAN profile",
+            "rough WAN profile",
+            "Docs/Ops/MultiplayerLatencyTestPlan.md",
+            "Unreal packet simulation",
+        ],
+        "AGRARIAN_DEVELOPMENT_ROADMAP.md": [
+            "[x] Add basic latency testing.",
+            "clean LAN",
+            "rough WAN",
+        ],
+    }
+
+    for relative_path, needles in checks.items():
+        try:
+            content = read(relative_path)
+            for needle in needles:
+                require(content, needle, relative_path)
+        except AssertionError as exc:
+            errors.append(str(exc))
+
+    if errors:
+        for error in errors:
+            print(f"ERROR: {error}", file=sys.stderr)
+        return 1
+
+    print("PASS: MVP latency testing plan and helper script are present.")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())