feat(physics): R5-V1 — port PositionManager/Sticky/Constraint + TargetManager (Core, unwired)

The retail movement-manager family the R4 MoveToManager port left as
do-not-invent seams (decomp §9f/§9g). Faithful C# ports of retail's
PositionManager facade + StickyManager + ConstraintManager + the
TargetManager voyeur system, with full conformance tests. NO wiring yet
— purely additive, no behavior change. Wiring (retiring TS-39 sticky +
AP-79 target adapter) is R5-V2/V3.

New Core classes (src/AcDream.Core/Physics/Motion/):
- StickyManager (0x00555400): follow-a-target steering. adjust_offset's
  dense x87 mush decoded via ACE (StickyRadius 0.3, StickyTime 1.0,
  follow speed ×5 / fallback 15) — speed-clamped signed-distance steer +
  bounded turn-to-face; 1 s watchdog; Ok→initialized / non-Ok→teardown.
- ConstraintManager (0x00556090): the server-position rubber-band leash.
  90% IsFullyConstrained jump gate + grounded linear brake taper.
  Structural only — acdream never ARMS it (retail arms from
  SmartBox::HandleReceivedPosition, which acdream lacks, with two x87
  constants BN elided). IsFullyConstrained stays false = TS-35 behavior;
  leash-arming + the unknown constants are a deferred issue.
- PositionManager facade (0x00555160): lazy Sticky/Constraint + fan-out.
- TargetManager (0x0051a370) + TargettedVoyeurInfo: the peer-to-peer
  voyeur subscription system (0.5 s throttle, 10 s staleness,
  send-on-drift-past-radius, dead-reckon GetInterpolatedPosition). A
  faithful superset of the AP-79 adapter — SetTarget subscribes ON the
  target; the target's HandleTargetting pushes updates back.
- IPhysicsObjHost: the CPhysicsObj back-pointer seam (position/velocity/
  radius/contact/GetObjectA + target-tracking fan-out) the App wires per
  entity in V2/V3. MotionDeltaFrame: mutable retail-Frame delta accumulator.

Supporting:
- TargetInfo extended to the full retail 10-field struct (additive
  defaults keep the R4 4-arg call sites compiling).
- MoveToMath: signed CylinderDistanceNoZ, NormalizeCheckSmall,
  GlobalToLocalVec.
- Rename: the misnamed AcDream.Core.Physics.PositionManager (a remote
  anim+interp per-frame combiner, NOT the retail facade) → RemoteMotion
  Combiner, freeing the name and removing the ambiguity that breaks every
  file importing both Physics + Physics.Motion (GameWindow will in V2/V3).

Tests: 42 new conformance cases (Sticky/Constraint/Position facade +
TargetManager incl. the full cross-entity voyeur round-trip). Full suite
4006 green (+2 skipped), no regressions.

Decomp + ACE cross-ref + port plan: docs/research/2026-07-03-r5-managers/.

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

src/AcDream.Core/Physics/Motion/PositionManager.cs

@@ -0,0 +1,102 @@
+using System;
+
+namespace AcDream.Core.Physics.Motion;
+
+/// <summary>
+/// R5 — port of retail's <c>PositionManager</c> facade (acclient.h:30952,
+/// struct #3468; decomp 0x00555160-0x005553d0,
+/// <c>r5-positionmanager-sticky-decomp.md</c>). A thin fan-out over three
+/// sub-managers: Interpolation, Sticky, Constraint. Owned 1:1 by the entity's
+/// <see cref="IPhysicsObjHost"/> (retail <c>CPhysicsObj::position_manager</c>,
+/// lazily created).
+///
+/// <para><b>Interpolation note:</b> retail's <c>adjust_offset</c> chains
+/// Interpolation → Sticky → Constraint. acdream's interpolation stage lives in
+/// <see cref="RemoteMotionCombiner"/> (the R5-renamed remote-motion combiner,
+/// formerly the misnamed <c>Physics.PositionManager</c>) and is NOT chained
+/// here in V1 — this facade owns only the two R5 targets (Sticky retires TS-39;
+/// Constraint is structural — see <see cref="ConstraintManager"/>). Folding the
+/// combiner in as the interp stage is a wiring-slice cleanup.</para>
+/// </summary>
+public sealed class PositionManager
+{
+    private readonly IPhysicsObjHost _host;
+
+    // Lazily created (retail: sticky on first StickTo, constraint on first
+    // ConstrainTo — 0x00555230 / 0x00555280).
+    private StickyManager? _sticky;
+    private ConstraintManager? _constraint;
+
+    public PositionManager(IPhysicsObjHost host)
+        => _host = host ?? throw new ArgumentNullException(nameof(host));
+
+    /// <summary>Exposed for wiring/tests — the lazily-created sub-managers
+    /// (null until first use).</summary>
+    public StickyManager? Sticky => _sticky;
+    public ConstraintManager? Constraint => _constraint;
+
+    /// <summary>Retail <c>PositionManager::StickTo</c> (0x00555230) — lazily
+    /// create the <see cref="StickyManager"/> and begin following
+    /// <paramref name="objectId"/>.</summary>
+    public void StickTo(uint objectId, float radius, float height)
+    {
+        _sticky ??= new StickyManager(_host);
+        _sticky.StickTo(objectId, radius, height);
+    }
+
+    /// <summary>Retail <c>PositionManager::UnStick</c> (0x005551e0) — forward
+    /// to the sticky sub-manager if it exists.</summary>
+    public void UnStick() => _sticky?.UnStick();
+
+    /// <summary>Retail <c>PositionManager::GetStickyObjectID</c>
+    /// (0x00555270).</summary>
+    public uint GetStickyObjectId() => _sticky?.TargetId ?? 0u;
+
+    /// <summary>Retail <c>PositionManager::ConstrainTo</c> (0x00555280) —
+    /// lazily create the <see cref="ConstraintManager"/> and arm the leash.
+    /// (Unused in acdream — no arming call site; see
+    /// <see cref="ConstraintManager"/>.)</summary>
+    public void ConstrainTo(Position anchor, float startDistance, float maxDistance)
+    {
+        _constraint ??= new ConstraintManager(_host);
+        _constraint.ConstrainTo(anchor, startDistance, maxDistance);
+    }
+
+    /// <summary>Retail <c>PositionManager::UnConstrain</c>
+    /// (0x005552b0).</summary>
+    public void UnConstrain() => _constraint?.UnConstrain();
+
+    /// <summary>Retail <c>PositionManager::IsFullyConstrained</c>
+    /// (0x005552c0) — false when no constraint sub-manager exists.</summary>
+    public bool IsFullyConstrained() => _constraint?.IsFullyConstrained() ?? false;
+
+    /// <summary>
+    /// Retail <c>PositionManager::HandleUpdateTarget</c> (0x005553d0) — only
+    /// the sticky sub-manager cares about live target positions (interpolation
+    /// and constraint don't). Fanned out from
+    /// <c>CPhysicsObj::HandleUpdateTarget</c>.
+    /// </summary>
+    public void HandleUpdateTarget(TargetInfo info) => _sticky?.HandleUpdateTarget(info);
+
+    /// <summary>
+    /// Retail <c>PositionManager::adjust_offset</c> (0x00555190) — chains the
+    /// sub-managers' contributions into the SAME <paramref name="offset"/>
+    /// accumulator, in retail order. Retail runs Interpolation → Sticky →
+    /// Constraint; acdream's interpolation stays in the separate remote-motion
+    /// combiner (see class note), so this chains Sticky → Constraint only.
+    /// Constraint is LAST because it clamps the already-composed displacement.
+    /// </summary>
+    public void AdjustOffset(MotionDeltaFrame offset, double quantum)
+    {
+        _sticky?.AdjustOffset(offset, quantum);
+        _constraint?.AdjustOffset(offset, quantum);
+    }
+
+    /// <summary>
+    /// Retail <c>PositionManager::UseTime</c> (0x00555160) — per-tick pump.
+    /// Retail order Interpolation → Constraint → Sticky; acdream runs the two
+    /// owned managers (constraint's UseTime is a retail no-op, so effectively
+    /// just the sticky 1 s watchdog).
+    /// </summary>
+    public void UseTime() => _sticky?.UseTime();
+}