feat(physics): C4 route 4b-3 — remote teleport + cell-less through the canonical placement

Flips the last remote classification (SetPosition: teleport-advanced and
cell-less) onto 4b-1's RuntimeRemotePlacementDriveController, runs retail's
teleport_hook before the placement, and deletes the legacy remote-teleport
machinery. Contract: docs/research/2026-08-04-c4-route-4b-3-contract.md.

Retail: MoveOrTeleport @0x00516330's branch @0x00516386 -> teleport_hook
@0x005163EF -> SetFlags(0x1012) @0x00516414 -> SetPosition @0x00516420 ->
return 1 @0x00516438. The hook @0x00514ED0 runs BEFORE the placement and
regardless of its outcome. Retail places this branch unconditionally, at any
distance and any contact state (arg4 is read only @0x0051638E, after the
branch) — which is what retires AP-137's cell-less enqueue-vs-place delta.

D1 — the classifier's cell-less input is now the PRE-merge committed cell.
Retail's predicate is `this_1->cell == 0`, the BODY's own cell at
MoveOrTeleport entry (this_1 is assigned from this @0x00516334). acdream fed
the POST-merge canonical.FullCellId, which RefreshSnapshot ->
RefreshDerivedState -> SetFullCell has already stamped with the accepted wire
cell; a zero wire cell fails validation into RejectedData first. The shipped
remote cell-less predicate was therefore dead code, not merely different from
remotePlacementRequired. Threaded via a builder overload; route 1's overload
is untouched. The graphical !IsSpatiallyVisible arm of
projectionRequiresTeleportHook is deleted — a presentation predicate with no
retail analogue that fired the teleport machinery on a routine hot path.

Deleted: RemoteTeleportController (605), RemoteTeleportPlacement (85),
RemoteShadowPlacementSynchronizer (49), their 1,709 lines of tests, the
remotePlacementRequired predicate, the TeleportHookRequired plumbing, the
legacy pre-operation ConstrainTo fallback, and the player arm's legacy
!IsGrounded fallback. Net -2,030 lines.

Structural fix (two independent Opus reviews, round 1 FAIL/FAIL): three of the
four MAJORs were one defect — OnPosition carried two parallel inline copies of
the routing tail (player-guid, NPC-guid) that had drifted. Extracted
RunRemoteArmTail (3 call sites) and ApplyWireAirborneLeftoverBookkeeping (2),
both branches now share one implementation.

  A1  ToConstraintArm mapped AirborneSnap -> AirborneNoOperation, so the NPC
      arm armed ConstrainTo ZERO times for an out-of-contact wire-grounded
      creature — a regression this slice introduced while closing a
      structurally identical hole. Now maps to NearInterpolate; switch made
      total with a throwing default proven unreachable.
  R1  D2's write-nothing shape existed on the player arm only; NPC packets
      fell through and wrote the body. Retail makes no player/NPC distinction.
  R2  report_collision_end(this,1) @0x00514F31 was bound to
      ShadowObjects.Suspend, a port of a DIFFERENT retail function
      (remove_shadows_from_cells) that teleport_hook never calls. Now routes
      to RuntimeCollisionReportingState.LeaveWorld, which wraps the private
      ForceEnd in an admission-blocking transaction so a DoCollisionEnd
      callback cannot recreate the contact table.
  R3/A2 A teleported NPC synthesized ServerVelocity from the teleport distance
      (~1,000+ m/s) and planned a run cycle from it. Both the install and
      RemoteServerControlledVelocityCycle.Apply now gate on !isTeleportRoute.

BISECT HAZARD — A1's fix is correct only BECAUSE R1 landed. AirborneSnap is
reachable wire-airborne on the NPC arm only while D2's shape is missing there.
Reverting R1 alone silently inverts A1 into the opposite divergence: arming
where retail returns 0. Revert both or neither.

Also in the velocity hunk: the NPC block's two !IsPlayerGuid(update.Guid)
guards were dropped when it was wrapped in `if (!isTeleportRoute)`. Safe — all
five exit paths of the enclosing IsPlayerGuid block return, so the predicate is
unconditionally false below it — but it was unremarked by both reviews.

Register: AP-137 REWRITTEN (not deleted) to the surviving acdream-only
divergences — null classification during the login window and Rejected*
through UnroutedCatchUp keep a row. AD-42's RemoteTeleportController citation
retired; AP-136/AP-138 writer lists corrected to the two surviving non-Position
rebucket writers; AP-138 gains the teleport arm as a second producer of the
visible-without-collision residual (retirement path remains #309). AP-135 is
untouched and its two airborne bookkeeping writes are preserved on both arms.
AP-131 does not retire; #276 does not close.

Proof obligation 1: ParkCollisionResidents' overlap throw stays unreachable —
the teleport arm adds packets to the same TryBeginExclusiveAuthoredPlacement
one-operation-per-key machinery the far arm uses, opens no new operation shape,
and every DeferredCell outcome cancels synchronously with
restoreCancelledPark: true. The guarded property remains
HasOldPrefixPlacementDebt's stall, not a throw (4b-1's B2 caveat stands).

Correction to an earlier claim: LiveEntityPresentationController's
_activePlacementOwners was NOT write-never at HEAD —
remotePlacementRequired -> BeginPlacement -> Begin -> BeginAuthoritativePlacement
was a live writer chain. It becomes write-never BECAUSE this slice deletes that
chain, which is why deleting the dead half is behaviour-preserving.

Probe: ACDREAM_PROBE_REMOTE_TELEPORT=1 emits one [remote-teleport] line per
routed arm (guid, cause, hook-ran, placement status). TEMPORARY, strip with the
probe family.

Carried, disclosed not fixed: no dedicated bidirectional collision-partner test
for R2 (the wiring, not LeaveWorld itself, is what lacks coverage); the
stress test's teleport step drives hand-written field assignments rather than
the canonical arm; the per-packet runTeleportHook closure allocation (network
path, not the resolve path Slice I's 0 B discipline governs — file before
route 5 adds a fourth call site). B2: IRuntimeCollisionReportObserver has zero
production implementations, so retail's bidirectional DoCollisionEnd half still
reaches no gameplay consumer — this fix closes the wrong-function binding, not
that nobody listens.

Complete Release suite MEASURED at 11,013 passed / 4 skipped / 0 failed
(baseline 11,027/4/0; net -14 = ~33 deleted test cases against ~19 added).
Neither known flake fired (#302 PortalProjectionTests GC-allocation, #308
NakEmissionTests wall-clock).

STILL OWED: the two-client connected gate, which MUST use an NPC/creature
teleport target. Both round-1 MAJORs lived on the NPC arm and the velocity
cycle early-returns for 0x50xxxxxx guids, so a player target structurally
cannot observe A1, A2, or R3.

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

tests/AcDream.Headless.Tests/HeadlessSessionHostTests.cs

@@ -508,7 +508,6 @@ public sealed class HeadlessSessionHostTests
             isLocalPlayer: true,
             forcePositionRotation: Quaternion.Identity,
             currentLocalVelocity: controller.BodyVelocity,
-            projectionRequiresTeleportHook: false,
             acknowledgeProjection: null,
             out PositionTimestampDisposition disposition,
             out _,