Add position smoothing and movement snapping

Introduce simple position smoothing for normal proxy movement and snap special movements. Adds kProxyPositionLerpAlpha, Lerp/LerpPosition helpers, and ShouldSnapRemoteMovement to lerp proxy position on normal updates while snapping on cell_change, worldspace_change, and teleport. Update MoveProxyToRemotePlayer to use lerp or snap, keep heading snapping (TODO: wrapped angle smoothing), and add throttled/readable logs for smoothing start, first smoothed movement, snaps, and idle-on-cell-mismatch. Minor messaging change on disconnect to leave proxy idle at last position. Update docs (architecture, setup, protocol) and dev log to reflect the new behavior and testing notes; dynamic spawning/multiple proxies remain out of scope.

docs/architecture.md

@@ -23,7 +23,9 @@ both send and receive paths:
 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`.
+    snapshot and moves the single placed proxy actor in `F4TTestCell01`,
+    smoothing normal movement and snapping cell changes, worldspace changes, and
+    teleports.
 
 The Fallout 4 plugin still does not dynamically spawn remote actors.
 
@@ -102,7 +104,6 @@ update path.
 
 - Remote actor spawning
 - Multiple proxy actors
-- Interpolation or smoothing
 - Combat sync
 - Quest sync
 - Inventory sync

docs/dev-log.md

@@ -644,3 +644,41 @@ Use this format for future updates:
 - Build the plugin with `xmake build`.
 - Run the single-client, two-client, and disconnect tests in `F4TTestCell01`.
 
+## 2026-06-02
+
+### What Changed
+
+- Added simple position smoothing for normal remote proxy movement.
+- Kept proxy actor movement on the `F4TProxyActorController` game-thread update
+  path using copied remote-player snapshots.
+- Kept the single-proxy, lowest-`playerId` selection behavior.
+- Added snap movement for `cell_change`, `worldspace_change`, and `teleport`
+  remote transforms.
+- Left rotation snapping in place with a TODO for wrapped angle smoothing.
+- Left the proxy idle at its last position when the represented remote player
+  disconnects, disappears, or leaves the same cell.
+- Added readable one-shot and throttled logs for smoothing, first smoothed
+  movement, special movement snaps, disappearance, and same-cell mismatch idle
+  behavior.
+
+### What Worked
+
+- Dynamic spawning and multiple proxy actors remain out of scope.
+- Networking still only updates plain remote-player state and does not touch
+  Fallout 4 actors or references.
+
+### What Broke
+
+- Not tested in-game yet.
+
+### Notes
+
+- Hiding or disabling the proxy actor is still deferred. The current safe
+  behavior is to leave the placed proxy idle at its last valid position.
+
+### Next Steps
+
+- Build the plugin with `xmake build`.
+- Run the single-client, two-client, special-movement, disconnect, and cell-leave
+  tests in `F4TTestCell01`.
+