fix(combat): escape occupied login positions

Port retail's radius-aware placement ring so a relogging player is seated beside creatures occupying the saved location, and register the local body in the shared resolved-shadow pipeline. Route new forward movement and jump through AbortAutomaticAttack so repeat combat cancels immediately on movement.

Co-Authored-By: Codex <codex@openai.com>

tests/AcDream.Core.Tests/Physics/InitialPlacementOverlapTests.cs

@@ -0,0 +1,86 @@
+using System.Numerics;
+using AcDream.Core.Physics;
+
+namespace AcDream.Core.Tests.Physics;
+
+/// <summary>
+/// Enter-world overlap conformance for retail
+/// <c>CTransition::find_placement_pos</c> (0x0050BA50).
+/// </summary>
+public sealed class InitialPlacementOverlapTests
+{
+    private const uint Landblock = 0xA9B40000u;
+    private const uint Cell = Landblock | 0x0001u;
+    private const uint PlayerId = 0x50000001u;
+    private const uint MonsterId = 0x50000002u;
+    private const float Radius = 0.48f;
+
+    [Fact]
+    public void PlayerReloggingInsideMonster_SearchesOutToNearestClearRing()
+    {
+        var engine = new PhysicsEngine { DataCache = new PhysicsDataCache() };
+        engine.AddLandblock(
+            Landblock,
+            new TerrainSurface(new byte[81], new float[256]),
+            Array.Empty<CellSurface>(),
+            Array.Empty<PortalPlane>(),
+            0f,
+            0f);
+
+        var savedFeet = new Vector3(10f, 10f, 0f);
+        var playerCenter = savedFeet + new Vector3(0f, 0f, Radius);
+        var monsterCenter = playerCenter + new Vector3(0.10f, 0f, 0f);
+
+        // Retail registers every placed CPhysicsObj, including the local
+        // player. The mover's OBJECTINFO::object self pointer excludes only
+        // its own shadow while the monster remains an obstruction.
+        RegisterSphere(engine, PlayerId, playerCenter,
+            EntityCollisionFlags.IsPlayer | EntityCollisionFlags.IsCreature);
+        RegisterSphere(engine, MonsterId, monsterCenter,
+            EntityCollisionFlags.IsCreature);
+
+        ResolveResult result = engine.ResolvePlacement(
+            savedFeet,
+            Cell,
+            sphereRadius: Radius,
+            sphereHeight: 1.835f,
+            stepUpHeight: 0.4f,
+            stepDownHeight: 0.4f,
+            moverFlags: ObjectInfoState.IsPlayer | ObjectInfoState.EdgeSlide,
+            movingEntityId: PlayerId);
+
+        Assert.True(result.Ok);
+        Assert.NotEqual(savedFeet, result.Position);
+        float centerDistance = Vector3.Distance(
+            result.Position + new Vector3(0f, 0f, Radius),
+            monsterCenter);
+        Assert.True(centerDistance >= Radius * 2f - PhysicsGlobals.EPSILON,
+            $"placement must clear the monster; centers remain {centerDistance:F3} m apart");
+        Assert.True(Vector3.Distance(savedFeet, result.Position) <= 4f,
+            "retail placement search is bounded to four metres");
+    }
+
+    private static void RegisterSphere(
+        PhysicsEngine engine,
+        uint id,
+        Vector3 center,
+        EntityCollisionFlags flags)
+    {
+        engine.ShadowObjects.Register(
+            id,
+            gfxObjId: 0u,
+            worldPos: center,
+            rotation: Quaternion.Identity,
+            radius: Radius,
+            worldOffsetX: 0f,
+            worldOffsetY: 0f,
+            landblockId: Landblock,
+            collisionType: ShadowCollisionType.Sphere,
+            cylHeight: 0f,
+            scale: 1f,
+            state: 0u,
+            flags: flags,
+            seedCellId: Cell,
+            isStatic: false);
+    }
+}