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.

plugin/include/F4TProxyActorController.h

@@ -2,7 +2,10 @@
 
 namespace F4T::ProxyActorController
 {
-	// Temporary game-thread-only actor-control safety test. This validates that the
-	// plugin can resolve and move the placed proxy before remote-player visual sync.
+	// Game-thread-only actor controller for the single placed proxy test actor.
+	// Networking threads must only update plain remote-player state.
+	void Update();
+
+	// Backward-compatible alias for the earlier local-player-offset safety test entry point.
 	void UpdateSafetyTest();
 }