feat: seed move speeds for pre-v22 creatures on load

A creature deserialized from a pre-v22 save whose think speeds still match
what it would spawn with today was never hand-tuned: adopt today's table
move values, so existing worlds and pets pick up npc-speeds pacing without
a respawn. A creature with tuned think speeds no longer matches and keeps
movement inheriting its think clock.

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

Projects/UOContent.Tests/Tests/Mobiles/AI/MoveSpeedTests.cs

@@ -24,16 +24,25 @@ public class MoveSpeedTests : IDisposable
 
     private sealed class SpeedStub : BaseCreature
     {
+        // Stands in for the npc-speeds table (unconfigured in the test fixture).
+        public double TableActiveMove;
+        public double TablePassiveMove;
+
         public SpeedStub() : base(AIType.AI_Animal) => Body = 0xC9;
 
         public SpeedStub(Serial serial) : base(serial) => Body = 0xC9;
 
-        // NPCSpeeds isn't configured in the test fixture; provide fixed think speeds.
         public override void GetSpeeds(out double activeSpeed, out double passiveSpeed)
         {
             activeSpeed = 0.3;
             passiveSpeed = 0.6;
         }
+
+        public override void GetMoveSpeeds(out double activeMoveSpeed, out double passiveMoveSpeed)
+        {
+            activeMoveSpeed = TableActiveMove;
+            passiveMoveSpeed = TablePassiveMove;
+        }
     }
 
     private SpeedStub NewCreature()
@@ -103,6 +112,33 @@ public class MoveSpeedTests : IDisposable
         Assert.Equal(0.9, bc.PassiveMoveSpeed); // other override untouched
     }
 
+    [Fact]
+    public void Migration_MatchingThinkSpeeds_AdoptTableMoveValues()
+    {
+        var bc = NewCreature(); // think 0.3/0.6, matching its table entry
+        bc.TableActiveMove = 0.45;
+        bc.TablePassiveMove = 0.9;
+
+        bc.MigrateMoveSpeeds();
+
+        Assert.Equal(0.45, bc.ActiveMoveSpeed);
+        Assert.Equal(0.9, bc.PassiveMoveSpeed);
+    }
+
+    [Fact]
+    public void Migration_TunedThinkSpeeds_KeepInheriting()
+    {
+        var bc = NewCreature();
+        bc.SetSpeed(0.35, 0.6); // hand-tuned: no longer matches the table entry
+        bc.TableActiveMove = 0.45;
+        bc.TablePassiveMove = 0.9;
+
+        bc.MigrateMoveSpeeds();
+
+        Assert.Equal(0.35, bc.ActiveMoveSpeed);
+        Assert.Equal(0.6, bc.PassiveMoveSpeed);
+    }
+
     [Theory]
     [InlineData(true)]
     [InlineData(false)]

Projects/UOContent/Mobiles/BaseCreature.cs

@@ -2230,6 +2230,10 @@ namespace Server.Mobiles
                 _activeMoveSpeed = reader.ReadDouble();
                 _passiveMoveSpeed = reader.ReadDouble();
             }
+            else
+            {
+                MigrateMoveSpeeds();
+            }
 
             if (version <= 14 && m_Paragon && Hue == 0x31)
             {
@@ -4988,6 +4992,20 @@ namespace Server.Mobiles
             NPCSpeeds.GetMoveSpeeds(this, out activeMoveSpeed, out passiveMoveSpeed);
         }
 
+        // Pre-v22 saves carry no movement clock. A creature whose serialized think speeds
+        // still match what it would spawn with today was never hand-tuned: adopt today's
+        // move values so existing worlds (and pets) pick up npc-speeds pacing without a
+        // respawn. Tuned creatures keep movement inheriting their think clock.
+        internal void MigrateMoveSpeeds()
+        {
+            GetSpeeds(out var activeSpeed, out var passiveSpeed);
+
+            if (_activeSpeed == activeSpeed && _passiveSpeed == passiveSpeed)
+            {
+                GetMoveSpeeds(out _activeMoveSpeed, out _passiveMoveSpeed);
+            }
+        }
+
         public virtual void DropBackpack()
         {
             var backpack = Backpack;