Add Walk To Player script and GUI controls

Add developer tooling to make GUI-managed fake clients run a Walk To Player script and provide UI controls.

Changes:
- server/fake_player.py: implement SCRIPT_WALK_TO_PLAYER, thread-safe script switching, pose/angle tracking, walk-to-player movement (straight-line, +150 X offset), target selection via a walk target provider, configurable send rates/speed/stop distance, and robust parsing of server client snapshots. Sends moving transforms ~10 Hz and falls back to idle keep-alives. Logs when no target is available.
- server/dev_server_app.py: add Set Idle and Walk To Player buttons, safe selected-client handling, and pass a client snapshot provider callback (server.get_clients()) to the fake player manager.
- server/README.md & docs/dev-log.md: document the new controls, behavior, testing notes, known limitations, and next steps.

Notes:
- Walk To Player picks the lowest non-fake playerId with a valid lastTransform and targets that player's last transform +150 X.
- Movement is simple straight-line stepping (no pathfinding/navmesh/obstacle avoidance).
- No protocol, plugin, server core, or existing fake_client networking behavior was changed.
- Quick static check: py_compile ran for relevant modules; manual GUI and in-game validation are still required.

docs/dev-log.md

@@ -1038,6 +1038,63 @@ Fake Clients tab or when the GUI server stops.
 
 ---
 
+## 2026-06-02 - Fake Client Walk To Player
+
+### Summary
+
+Added Fake Clients tab movement controls and a first useful fake-client movement
+script. GUI-managed fake clients can now be set to Idle or Walk To Player while
+remaining ordinary external TCP clients that send normal transform packets
+through the Python server.
+
+### Files Changed
+
+- `server/fake_player.py`
+- `server/dev_server_app.py`
+- `server/README.md`
+- `docs/dev-log.md`
+
+### Details
+
+- Added `Idle` and `Walk To Player` script modes to `FakePlayerClient`.
+- Added thread-safe script switching, pose tracking, and target state for
+  GUI-managed fake clients.
+- Added `Set Idle` and `Walk To Player` buttons to the Fake Clients tab.
+- Added safe selected-client handling with readable logs when no fake client is
+  selected or the server is stopped.
+- Walk To Player reads `FalloutTogetherServer.get_clients()` snapshots through a
+  manager callback, filters out GUI-managed fake clients, and targets the lowest
+  real `playerId` with a valid `lastTransform`.
+- Walk To Player moves in a straight line toward the real player's latest
+  transform plus a +150 X offset, sends moving transforms at about 10 Hz, and
+  returns to low-rate idle keep-alive transforms after reaching the stop
+  distance.
+- No plugin code, protocol fields, `server/server.py`, or `server/fake_client.py`
+  were changed.
+
+### Testing
+
+- Ran `python -m py_compile server.py server_core.py client_session.py
+  fake_client.py dev_server_app.py fake_player.py` from `server`; it succeeded.
+- Still needs manual GUI validation with `python dev_server_app.py`.
+- Still needs in-game Fallout 4/F4SE validation in `F4TTestCell01`.
+
+### Known Issues
+
+- Walk To Player uses simple straight-line movement only; it does not perform
+  pathfinding, navmesh checks, or obstacle avoidance.
+- Additional fake-client scripts are still future work.
+
+### Next Steps
+
+- Manually validate the GUI buttons with no real player connected and with a
+  Fallout 4 client in `F4TTestCell01`.
+- Add future dev/test scripts such as Walk Circle, Walk Square, Follow Player,
+  Jump Loop, Sneak Toggle, Teleport Test, Leave Cell / Return, and Disconnect
+  After Delay.
+
+---
+
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