Move placed proxy from remote-player snapshot

Enable game-thread proxy actor movement driven by a copied remote-player snapshot and update related networking/validation, docs, and test client.

- Plugin: add F4T::ProxyActorController::Update() (alias UpdateSafetyTest preserved) and implement remote-state-driven movement for the single placed proxy (F4TProxyRemotePlayer01REF) in F4TTestCell01. Selects lowest available playerId, validates same-cell/worldspace for movement, and caches represented playerId. Adds helper functions (ParseHexFormId, IsRemotePlayerInSameLocation, SelectRemotePlayerToRepresent, MoveProxyToRemotePlayer) and improved throttled logging.
- Networking: tighten transform packet required-field checking (requires type, playerId, x, y, z, angleZ, cellId), add GetMissingRequiredTransformField, make movementType/worldspaceId/clientTime/serverTime optional with sensible defaults, and switch LogThrottledWarning to accept string_view.
- main.cpp: call ProxyActorController::Update on game-thread tasks.
- fake_client.py: mirror new packet validation and provide defaults for optional fields.
- Docs/dev-log/protocol/setup: update architecture, dev log, protocol, and setup notes to describe the single-proxy remote-state milestone, required packet fields, and testing checklist.

This change keeps networking thread limited to parsing/updating plain remote-player state and moves all actor access to the game-thread controller. Dynamic spawning, multiple proxies, and interpolation remain out of scope.

docs/architecture.md

@@ -22,8 +22,10 @@ both send and receive paths:
 8. The server broadcasts `disconnect` packets when clients disconnect.
 9. The plugin and fake client remove disconnected players from their remote
    player tables.
+10. On the game-thread update path, the plugin reads a copied remote-player
+    snapshot and moves the single placed proxy actor in `F4TTestCell01`.
 
-The Fallout 4 plugin still does not spawn or move remote actors.
+The Fallout 4 plugin still does not dynamically spawn remote actors.
 
 ## Main Components
 
@@ -36,10 +38,11 @@ The native plugin is responsible for:
 - Sending local player data to the server
 - Receiving server packets on a background thread
 - Storing assigned and remote `playerId` state internally
+- Moving the single placed test proxy actor from remote-player state on the game
+  thread
 
 Planned later:
 
-- Applying remote player updates safely
 - Spawning or moving remote actors
 
 ### External Server
@@ -86,17 +89,20 @@ Current approach:
 ```text
 Networking thread receives packets
 Networking thread stores remote player state
-Game update reads remote player state
-Future game update applies actor movement
+Game update reads a copied remote player snapshot
+Game update moves the placed test proxy actor
 ```
 
 The networking receive thread does not directly modify Fallout 4 actors or game
 objects. It parses newline-separated JSON, updates plain C++ remote-player
-state, and leaves actor spawning or movement for a later game-thread milestone.
+state, and leaves actor access to `F4TProxyActorController` on the game-thread
+update path.
 
 ## Out Of Scope For Current Prototype
 
 - Remote actor spawning
+- Multiple proxy actors
+- Interpolation or smoothing
 - Combat sync
 - Quest sync
 - Inventory sync

docs/dev-log.md

@@ -606,4 +606,41 @@ Use this format for future updates:
 - Replace local-player-offset movement with remote player state movement.
 - Only move the proxy when the remote player is in the same cell/worldspace.
 - Snap movement first.
-- Add smoothing/interpolation later.
+- Add smoothing/interpolation later.
+
+## 2026-05-31
+
+### What Changed
+
+- Changed the proxy actor controller plan from local-player-offset movement to
+  remote-state-driven movement.
+- The placed proxy actor `F4TProxyRemotePlayer01REF` now represents the lowest
+  available remote `playerId` from a copied remote-player snapshot.
+- Proxy movement remains game-thread-only and throttled to roughly 5 Hz.
+- The networking receive thread still only parses packets and updates plain
+  remote-player state.
+- Relaxed receive-side transform validation so interior/test-cell packets only
+  require `cellId`; missing `worldspaceId` is stored as an empty string.
+- Added a same-test-cell proxy movement log for `F4TTestCell01`.
+
+### What Worked
+
+- Existing proxy actor lookup and safe handle caching were preserved.
+- The local-player-offset safety movement remains available as a debug fallback
+  mode in code.
+
+### What Broke
+
+- Not tested in-game yet.
+
+### Notes
+
+- The proxy is left wherever it last moved after a remote disconnect for now.
+- Dynamic spawning, multiple proxy actors, interpolation, and gameplay sync are
+  still intentionally out of scope.
+
+### Next Steps
+
+- Build the plugin with `xmake build`.
+- Run the single-client, two-client, and disconnect tests in `F4TTestCell01`.
+