Add fake-client dev scripts and GUI actions

Add developer-only fake-client scripts and UI actions for testing proxy behavior. Files updated: server/fake_player.py, server/dev_server_app.py, server/README.md, docs/dev-log.md. New scripts/actions: Walk Circle, Jump Once, Toggle Sneak, Leave Cell (Left Cell), Return To Cell, and Teleport Test. UI: added buttons and handlers in the DevServerWindow to trigger these actions. fake_player: implemented script/state handling, one-shot jump thread, teleport toggle, sneak flag, walk-circle movement, cell change transforms, a socket send lock, and protection for one-shot/action state. README and dev log updated with usage, testing notes, and known issues. Basic headless smoke tests and py_compile checks were performed; full in-game Fallout 4/F4SE validation remains manual.

docs/dev-log.md

@@ -1095,6 +1095,72 @@ through the Python server.
 
 ---
 
+## 2026-06-02 - Fake Client Test Scripts
+
+### Summary
+
+Added developer-only fake-client test scripts and actions to the PySide6 Fake
+Clients tab. GUI-managed fake clients can now test jump state, sneak state,
+circle movement, cell mismatch holding, return-to-cell behavior, and teleport
+snapping without launching multiple Fallout 4 instances.
+
+### Files Changed
+
+- `server/fake_player.py`
+- `server/dev_server_app.py`
+- `server/README.md`
+- `docs/dev-log.md`
+
+### Details
+
+- Added `Walk Circle` and `Left Cell` continuous fake-client modes.
+- Added one-shot `Jump Once`, `Toggle Sneak`, `Return To Cell`, and
+  `Teleport Test` actions.
+- Kept fake clients as external TCP clients that send normal newline-separated
+  JSON transform packets through the existing server socket.
+- Preserved the existing `Idle` and `Walk To Player` controls.
+- Added Fake Clients tab buttons for `Jump Once`, `Toggle Sneak`, `Walk Circle`,
+  `Leave Cell`, `Return To Cell`, and `Teleport Test`.
+- Kept Fake Clients table columns unchanged while continuing to refresh script,
+  cell, and position snapshots from the manager.
+- Added a socket send lock and protected script, pose, movement flags, and
+  one-shot action state with the existing client lock.
+- Left the Fallout 4 plugin, protocol, `server/server.py`, `server/fake_client.py`,
+  and server networking behavior unchanged.
+
+### 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.
+- Checked editor diagnostics for `server/fake_player.py` and
+  `server/dev_server_app.py`; no linter errors were reported.
+- Ran a headless smoke test on alternate local port `7788`; a GUI-managed fake
+  client connected through the real server socket and exercised Walk Circle,
+  Toggle Sneak, Jump Once, Leave Cell, Return To Cell, and Teleport Test without
+  disconnecting.
+- Not yet run: `python server.py` terminal launcher smoke test.
+- Not yet run: `python dev_server_app.py`, start the server, add/remove fake
+  clients, and click each Fake Clients script/action button.
+- Not yet run: Fallout 4/F4SE validation inside `F4TTestCell01` that Walk
+  Circle, Jump Once, Toggle Sneak, Leave Cell, Return To Cell, and Teleport Test
+  produce the expected proxy behavior.
+
+### Known Issues
+
+- Full Fallout 4/F4SE validation still needs to be run manually.
+- Walk Circle is a simple mathematical circle only; it does not use pathfinding,
+  navmesh, or obstacle avoidance.
+
+### Next Steps
+
+- Manually validate the GUI scripts with a real Fallout 4 client in
+  `F4TTestCell01`.
+- Consider future fake-client scripts such as Walk Square, Follow Player, Sprint
+  Toggle, Weapon Drawn Toggle, Disconnect After Delay, and multi-fake-player
+  choreography.
+
+---
+
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