Add proxy visual sneak scaffolding

Introduce default-off scaffolding for proxy visual sneak experiments: add kEnableProxyVisualSneakSync and kEnableProxyVisualSneakExperimentalGraph flags (false), include ACTOR_STANCE, and add a non-mutating ApplyProxyVisualSneakIfEnabled helper that reads proxy sneak/stance/forceSneak and emits one-time diagnostics when visual sneak is disabled. Add per-slot tracking fields (hasAppliedVisualSneakingState, hasLoggedVisualSneakDisabled, lastAppliedVisualSneakingState), ResetSlotVisualSneakTracking and calls to reset tracking when holding/reusing/disconnecting slots, and switch UpdateProxyAnimationStateDebug to accept a non-const RE::Actor&. Update docs/dev-log.md with an entry describing the change. Comments/TODOs note a future, separately approved experiment to call RE::Actor::SetSneaking(...) behind a disabled gate; current scaffolding intentionally avoids mutating actors, animation graph writes/events, or AI/package crouch logic. Build tested locally (plugin rebuild).

docs/dev-log.md

@@ -2314,6 +2314,67 @@ each remote `playerId` without visually applying animation.
 
 ---
 
+## 2026-06-03 - Proxy Visual Sneak Scaffolding
+
+### Summary
+
+Added default-off runtime proxy visual sneak scaffolding so future sneak/crouch
+visual experiments have isolated slot-local gates and reset tracking without
+mutating actors by default.
+
+### Files Changed
+
+- `plugin/src/F4TProxyActorController.cpp`
+- `docs/dev-log.md`
+
+### Details
+
+- Added default-off `kEnableProxyVisualSneakSync` and
+  `kEnableProxyVisualSneakExperimentalGraph` flags near the existing proxy
+  controller constants.
+- Added runtime-proxy-slot visual sneak tracking separate from existing
+  animation debug observation state.
+- Added a runtime-proxy-only game-thread helper that reads proxy-side
+  `IsSneaking()`, stance, and `forceSneak` diagnostics and logs once per slot
+  when no visual sneak method is enabled.
+- Kept the helper non-mutating with the default flags. It does not call
+  animation graph events, write animation graph variables, call `PerformAction`,
+  write `ActorState`, or use package/procedure/AI crouch behavior.
+- Left a TODO for a separately approved future experiment using
+  `RE::Actor::SetSneaking(remoteState.isSneaking)` behind the existing disabled
+  gate.
+- Reset visual sneak tracking through the existing slot observation reset path,
+  when runtime proxies are moved to holding, and when disconnected slots become
+  reusable.
+- Left networking, protocol, Python server code, fake-client tooling, placed
+  fallback behavior, runtime spawning, movement smoothing, snap behavior,
+  same-cell gating, held/reusable lifecycle, and combat/AI neutralization
+  unchanged.
+
+### Testing
+
+- Ran `xmake build` from `plugin`; it succeeded and rebuilt
+  `Fallout4Together.dll`.
+- Pending manual validation: use the Dev Server GUI to add fake clients, toggle
+  sneak on/off, and confirm existing animation debug logs plus one-time disabled
+  visual sneak diagnostics without any visual crouch by default.
+
+### Known Issues
+
+- Visual sneak/crouch application remains intentionally unimplemented.
+- The safe visual writer candidate still needs a manually approved
+  `RE::Actor::SetSneaking(...)` experiment before any proxy crouch behavior is
+  enabled.
+
+### Next Steps
+
+- Manually validate fake-client sneak toggles in `F4TTestCell01`.
+- If approved later, test `RE::Actor::SetSneaking(...)` behind the disabled
+  visual sneak gate with explicit clear handling for false, disconnect, hold,
+  reassignment, and reuse.
+
+---
+
 ## Entry Template
 
 Use this format for future updates: