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/MoveToMath.cs

@@ -230,6 +230,58 @@ public static class MoveToMath
         return edgeDist > 0f ? edgeDist : 0f;
     }
 
+    /// <summary>
+    /// Retail <c>Position::cylinder_distance_no_z</c> — the <b>signed</b>
+    /// horizontal (X/Y) edge-to-edge distance between two cylinders:
+    /// <c>centerDist − ownRadius − targetRadius</c>. Unlike
+    /// <see cref="CylinderDistance"/> (the arrival-gate variant, which CLAMPS at
+    /// 0), this variant is NOT clamped — overlapping cylinders report a NEGATIVE
+    /// value. <c>StickyManager::adjust_offset</c> (0x00555430) relies on the
+    /// sign: when the follower is inside the desired 0.3 m stick gap the
+    /// distance goes negative, the per-tick delta inverts, and the mover backs
+    /// off to restore the gap (ACE StickyManager.cs:156).
+    /// </summary>
+    public static float CylinderDistanceNoZ(
+        float ownRadius, Vector3 ownPos, float targetRadius, Vector3 targetPos)
+    {
+        float dx = targetPos.X - ownPos.X;
+        float dy = targetPos.Y - ownPos.Y;
+        float centerDist = MathF.Sqrt(dx * dx + dy * dy);
+        return centerDist - ownRadius - targetRadius;
+    }
+
+    /// <summary>
+    /// Retail <c>AC1Legacy::Vector3::normalize_check_small</c> — normalize
+    /// <paramref name="v"/> in place, returning <c>true</c> if the vector was
+    /// too small to normalize (near-zero) and leaving it unchanged in that
+    /// case. Consumed by <c>StickyManager::adjust_offset</c> (don't chase
+    /// jitter when already at the target) and
+    /// <see cref="TargetManager.ReceiveUpdate"/> (interpolated-heading
+    /// fallback). A public shared twin of the private helper in
+    /// <c>ParticleSystem</c>; same 1e-8 near-zero length guard.
+    /// </summary>
+    /// <returns><c>true</c> = too small (left unchanged); <c>false</c> =
+    /// normalized.</returns>
+    public static bool NormalizeCheckSmall(ref Vector3 v)
+    {
+        float length = v.Length();
+        if (length < 1e-8f)
+            return true;
+        v /= length;
+        return false;
+    }
+
+    /// <summary>
+    /// Retail <c>Position::globaltolocalvec</c> — rotate a WORLD-space vector
+    /// into a frame's LOCAL coordinates by the inverse of the frame's
+    /// orientation. Consumed by <c>StickyManager::adjust_offset</c>
+    /// (0x00555430) to express the self→target offset in the mover's own frame
+    /// before flattening Z and steering. Pure rotation (no translation) —
+    /// <paramref name="worldVec"/> is a direction/offset, not a point.
+    /// </summary>
+    public static Vector3 GlobalToLocalVec(Quaternion frameOrientation, Vector3 worldVec)
+        => Vector3.Transform(worldVec, Quaternion.Conjugate(frameOrientation));
+
     /// <summary>
     /// Landblock-local wire origin → world space (verbatim relocation from
     /// the deleted <c>RemoteMoveToDriver.OriginToWorld</c>, R4-V4): MoveTo /