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).

docs/research/2026-07-30-constraint-leash-constants.md

@@ -94,3 +94,52 @@ None for the constants/flow. Remaining implementation risk is only
 where acdream's position-acceptance seams sit today (J6.3 moved
 teleport correlation into Runtime — the implementer must find the
 current owner rather than trusting older file cites).
+
+## As-ported (Campaign P Slice P5, 2026-07-30)
+
+The implementation risk flagged above resolved to these CURRENT seam owners
+(post-J-slices) — recorded here so the next reader doesn't have to re-derive
+them:
+
+- **Constants** — `src/AcDream.Core/Physics/Motion/ConstraintDistance.cs`.
+  Keyed purely on the object's own full cell id's low 16 bits (`>= 0x0100` =
+  indoor); the vestigial player/remote branch from §1 is deliberately not
+  represented as an API parameter.
+- **Remote arm** — `src/AcDream.App/Physics/LiveEntityNetworkUpdateController.cs`,
+  the inbound `UpdatePosition` handler's remote branch (`update.Guid !=
+  _playerServerGuid`), immediately after the `remotePlacementRequired`
+  hard-teleport block returns (that block already covers retail's
+  `MoveOrTeleport` Branch A / hard-place case; everything reached past it is
+  "did not hard-place"). One call site covers BOTH player-remote and NPC
+  remotes — retail's `SmartBox::HandleReceivedPosition` doesn't distinguish
+  them either, only `GetStart/MaxConstraintDistance`'s now-omitted vestigial
+  branch did. Anchored to the live `IPhysicsObjHost.Position` (which reads
+  `RemoteMotion.Body.Position` + the tracked cell id), matching retail's
+  "anchored to the object's own current position" — since the anchor and
+  `_host.Position` read are the same value at call time,
+  `ConstraintManager.ConstrainTo`'s initial offset is always 0 regardless of
+  whether the routing above just far-snapped or left a near-correction
+  queued.
+- **Remote per-tick taper + `IsFullyConstrained` push** — already wired
+  pre-P5 for the taper (`RuntimeRemotePhysicsUpdater.Tick`/`TickHidden` call
+  `PositionManager.AdjustOffset` every tick via the pre-existing R5-V3
+  sticky/constraint chain); P5 added the `PhysicsBody.IsFullyConstrained =
+  host.PositionManager.IsFullyConstrained()` push at the same two call
+  sites, since `MotionInterpreter` only holds a `PhysicsBody` (no host
+  reference) and needs a live value to read.
+- **Local player arm** — `src/AcDream.Runtime/Gameplay/PlayerMovementController.cs`:
+  `SetPositionCore` (teleport: `UnConstrain` then re-`ConstrainTo` after the
+  existing `StopCompletelyAtPhysicsObjectBoundary` velocity zero — composed,
+  not duplicated) and `CommitPreparedPosition` (mirrors the same pair for
+  the deferred player-mode-entry commit path); `BlipPosition` (ForcePosition:
+  `ConstrainTo` only, no teardown — matches `SmartBox::BlipPlayer` surviving
+  motion/velocity/stick). Anchored to `_body.CellPosition` (the just-applied
+  received position).
+- **Local player per-tick taper + push** — `PlayerMovementController.Update`
+  already called `PositionManager.AdjustOffset` every physics tick pre-P5;
+  P5 added the `_body.IsFullyConstrained = PositionManager?.IsFullyConstrained()
+  ?? false` push immediately after, at the same chokepoint.
+- **TS-35 retirement** — `PhysicsBody.IsFullyConstrained` stayed a plain
+  settable bool (not a computed property) so the ~40 pre-existing direct-set
+  unit tests keep working; the per-tick pumps above are its single writers
+  now, matching the project's per-entity single-owner-write pattern.