fix(B.6+B.7): arrival predicate uses safety margin INSIDE ACE's WithinUseRadius

Trace showed local arrival landing at 3.025 m from a target with
objDist=3.00. The previous arrival used ArrivalEpsilon=0.05 to
EXPAND the threshold (dist <= 3.05), so the body stopped right at
the boundary. ACE's server-side WithinUseRadius is strict
(dist <= radius), so 3.025 > 3.00 — ACE rejected the re-sent
action and looped back to MoveToObject. User had to manually
re-press R because auto-arrival kept landing just-outside-range.

Fix: walk INSIDE ACE's radius by a safety margin (0.3–0.5 m, capped
at 40 % of threshold so tight pickup radii like 0.6 m stay
reachable).

  arrivalThreshold = wire's distanceToObject or minDistance
  safetyMargin     = min(0.5, arrivalThreshold * 0.4)
  effectiveArrival = max(arrivalThreshold - safetyMargin, 0.1)

  Examples:
    objDist=3.00 (NPC) → walk to ≤2.50 m  (ACE happy at 3.0)
    objDist=2.00 (door) → walk to ≤1.50 m
    objDist=0.60 (item) → walk to ≤0.36 m
    objDist=0.50 (small) → walk to ≤0.30 m

Flee case (moveTowards=false) keeps its original predicate with
+ArrivalEpsilon — that's the boundary check semantics for fleeing
to a min-distance, not a max-distance use radius.

src/AcDream.App/Input/PlayerMovementController.cs

@@ -445,15 +445,24 @@ public sealed class PlayerMovementController
         float dy = _autoWalkDestination.Y - pos.Y;
         float dist = MathF.Sqrt(dx * dx + dy * dy);
 
-        // Arrival predicate (RemoteMoveToDriver convention; matches retail).
+        // Arrival predicate. CRITICAL: ACE's server-side WithinUseRadius
+        // is strict (dist <= radius), so arriving exactly at the radius
+        // boundary fails — ACE rejects the action and replies with
+        // another MoveToObject. To ensure the re-sent action lands
+        // INSIDE ACE's radius, we apply a safety margin that walks
+        // 0.3–0.5 m past the boundary (capped to 40 % of the threshold
+        // so tight pickup radii like 0.6 m stay reachable without
+        // collapsing to zero).
         float arrivalThreshold = _autoWalkMoveTowards
             ? _autoWalkDistanceToObject
             : _autoWalkMinDistance;
+        float safetyMargin    = MathF.Min(0.5f, arrivalThreshold * 0.4f);
+        float effectiveArrival = MathF.Max(arrivalThreshold - safetyMargin, 0.1f);
         bool arrived =
             (_autoWalkMoveTowards
-                && dist <= arrivalThreshold + RemoteMoveToDriver.ArrivalEpsilon)
+                && dist <= effectiveArrival)
          || (!_autoWalkMoveTowards
-                && dist >= arrivalThreshold - RemoteMoveToDriver.ArrivalEpsilon);
+                && dist >= arrivalThreshold + RemoteMoveToDriver.ArrivalEpsilon);
         if (arrived)
         {
             EndServerAutoWalk("arrived");