Stage 1: walk while healing legs, for SPT 4.0.13

Ground-up reimplementation of yox92/SmartAction targeting SPT 4.0.13 /
EFT 0.16.9.0.40087. Only the walk-while-healing feature is implemented;
see NOTES.md for status and the deferred sprint work.

Design departures from upstream:

- CanWalk is a guarded postfix, not a transpiler. Upstream rewrote the
  method body, which affects every MovementContext in the raid including
  bots, and is hard-incompatible with the three other mods already
  patching MovementContext in a typical load order (SAIN, ORBIT,
  maschine-DualSideDoorBreach). A postfix that only flips false -> true
  for IsYourPlayer is inert for other entities by construction.

- The postfix re-tests ObstacleCollisionFacade_1.CanMove() before
  lifting. Upstream's transpiler dropped that check along with the
  HealingLegs check, silently disabling obstacle blocking.

- Targets resolve by name via AccessTools.PropertyGetter + nameof rather
  than by GClass number, so they survive EFT version bumps.

Verified in-game against 78 loaded plugins: both patches attach, the
guard rejected 985 non-local MovementContext calls with zero leaks, and
_player was never null across ~4000 guard calls.

CanSprintPatch is parked in deferred/ rather than deleted:
MovementContext.CanSprint does not gate sprinting (EnableSprint calls
Physical.Sprint unconditionally), and forcing it true makes EnableSprint
run ForceStopInteractions()/RemoveLeftHandItem() mid-heal. Details and
the 3.11 -> 4.0.13 rename table are in NOTES.md.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Patch/MovementPatchUtil.cs

@@ -0,0 +1,47 @@
+using System.Reflection;
+using EFT;
+using HarmonyLib;
+
+namespace SmartAction.Patch;
+
+internal static class MovementPatchUtil
+{
+    // MovementContext._player is protected, so it needs reflection. Resolved once at
+    // type-init rather than per call — these postfixes run on every movement query.
+    private static readonly FieldInfo PlayerField = AccessTools.Field(typeof(MovementContext), "_player");
+
+    /// <summary>
+    /// True only for the player this client controls.
+    ///
+    /// Every bot and, under Fika, every remote player owns its own MovementContext, and these
+    /// postfixes fire for all of them. Gating on IsYourPlayer is what keeps the patches inert
+    /// for everyone else — it is the entire multiplayer-safety story for Stage 1.
+    /// </summary>
+    internal static bool IsLocalPlayer(MovementContext context)
+    {
+        var value = PlayerField?.GetValue(context);
+
+        // Fast path when instrumentation is off: no counters, no branches beyond the check.
+        if (!Diagnostics.Enabled)
+        {
+            return value is Player { IsYourPlayer: true };
+        }
+
+        if (value is not Player player)
+        {
+            // Predicted failure mode: a MovementContext whose _player is not yet assigned
+            // (bot mid-spawn). The pattern match absorbs it rather than throwing an NRE.
+            Diagnostics.NullPlayerCalls++;
+            Diagnostics.OnceNullPlayer();
+            Diagnostics.Tick();
+            return false;
+        }
+
+        var isLocal = player.IsYourPlayer;
+        if (isLocal) Diagnostics.LocalCalls++;
+        else Diagnostics.NonLocalCalls++;
+
+        Diagnostics.Tick();
+        return isLocal;
+    }
+}