fix(physics): P5 commit 3 - retire TS-35, close #167 (ConstraintManager leash)

PhysicsBody.IsFullyConstrained now reflects real ConstraintManager state
(pushed every tick by the same per-tick pumps commit 2 wired), so
jump_is_allowed's already-ported gate (WeenieError 0x47) actually fires
while an object is rubber-banding hard against a server position
correction, closing the last piece of #167.

Housekeeping:
- Delete register row TS-35 (retired: the write side is no longer stubbed).
- Rewrite the stale doc comments on PhysicsBody.IsFullyConstrained,
  ConstraintManager (class + IsFullyConstrained), PositionManager.ConstrainTo,
  EntityPhysicsHost.PositionManager, and PlayerMovementController.PositionManager
  that described the leash as permanently unarmed/stubbed.
- Close #167 in ISSUES.md citing the research doc and commits e0629145 /
  7719d25b.
- Add an "as-ported" addendum to
  docs/research/2026-07-30-constraint-leash-constants.md naming the actual
  current seam owners (the doc's own open question flagged this as
  implementer-verify-required post-J-slices).
- Update docs/plans/2026-07-29-physics-parity-campaign.md's P5 status and
  CLAUDE.md's Campaign P summary to reflect #167's closure (items #153/#72
  remain open in P5).

Verification: complete solution suite green - 9,978 tests, 5 skips, 0
failures across all 9 test projects (Core.Tests, Runtime.Tests, App.Tests,
Headless.Tests, Core.Net.Tests, Content.Tests, UI.Abstractions.Tests,
Bake.Tests, Cli.Tests).

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

@@ -13,16 +13,18 @@ namespace AcDream.Core.Physics.Motion;
 /// <c>CMotionInterp::jump_is_allowed</c> (block jump while
 /// <see cref="IsFullyConstrained"/>).
 ///
-/// <para><b>Arming is UNPORTED in acdream (R5).</b> Retail arms the leash ONLY
-/// from <c>SmartBox::HandleReceivedPosition</c> (on every inbound server
-/// position packet) with two constants from
-/// <c>CPhysicsObj::GetStart/MaxConstraintDistance</c> whose values BN elided
-/// (x87 returns — unknown, need a cdb read). acdream's position reconciliation
-/// is not SmartBox, so nothing calls <see cref="ConstrainTo"/> — the leash
-/// stays disarmed and <see cref="IsFullyConstrained"/> stays false, matching
-/// register TS-35's current stub behavior. The class is ported for structural
-/// completeness of <see cref="PositionManager"/>; the leash-arming port + the
-/// two unknown constants are a deferred issue (port-plan §Constraint scope).</para>
+/// <para><b>Armed as of Campaign P P5 (2026-07-30, #167, closed
+/// register row TS-35).</b> Retail arms the leash ONLY from
+/// <c>SmartBox::HandleReceivedPosition</c> (0x00453fd0, on every inbound
+/// server position packet) with the start/max band from
+/// <c>CPhysicsObj::GetStart/MaxConstraintDistance</c> — byte-decoded (the x87
+/// returns BN elided) in <see cref="ConstraintDistance"/>. acdream's
+/// equivalents call <see cref="ConstrainTo"/> at every accepted-position
+/// seam: <c>LiveEntityNetworkUpdateController</c> for remotes (anchored to
+/// the object's own position, right after the hard-teleport branch returns)
+/// and <c>PlayerMovementController.SetPosition</c>/<c>BlipPosition</c> for
+/// the local player (anchored to the received position). See
+/// <c>docs/research/2026-07-30-constraint-leash-constants.md</c>.</para>
 /// </summary>
 public sealed class ConstraintManager
 {
@@ -77,8 +79,11 @@ public sealed class ConstraintManager
     /// Retail <c>ConstraintManager::IsFullyConstrained</c> (0x005560d0):
     /// <c>constraint_distance_max * 0.9 &lt; constraint_pos_offset</c> — the
     /// object counts as fully constrained once it has strained past 90 % of the
-    /// max leash. Read by <c>jump_is_allowed</c> to block jumps. Always false
-    /// while the leash is disarmed (acdream never arms it — see class note).
+    /// max leash. Read by <c>jump_is_allowed</c> to block jumps. False while
+    /// unconstrained (no prior <see cref="ConstrainTo"/> or after
+    /// <see cref="UnConstrain"/>) since <see cref="ConstraintDistanceMax"/> and
+    /// <see cref="ConstraintPosOffset"/> both default to zero (<c>0*0.9 &lt; 0</c>
+    /// is false).
     /// </summary>
     public bool IsFullyConstrained()
         => ConstraintDistanceMax * 0.9f < ConstraintPosOffset;