refactor(physics): delete legacy PhysicsEngine.Resolve/ResolvePlacement/HasCellSurface (C5a, AP-1/AD-1)

Member-wise deletion of the three legacy resolver members named in
docs/research/2026-08-05-c5a-contract.md: PhysicsEngine.Resolve,
PhysicsEngine.HasCellSurface, and PhysicsEngine.ResolvePlacement. An
exhaustive receiver census over src/ found zero production callers of any
of the three — every production placement writer already reaches the
canonical PhysicsEngine.SetPosition transaction exclusively through
RuntimeSetPositionState (three call sites total). The deletion is purely
member-wise: IsSpawnCellReady and AdjustPosition, which shared the same
source region as the deleted members, are preserved byte-identical — every
remaining production caller of either (including PhysicsCameraCollisionProbe,
AdjustPosition's sole surviving production caller) is unaffected.

Companion changes:
- PlayerMovementController's 3-argument SetPosition test overload is renamed
  to SeedPlacementForTest (internal) and CommitPreparedPosition is deleted;
  83 call sites across 19 test files were mechanically renamed to match.
- Seven pinned test dispositions from the contract are executed:
  3.1 (PhysicsEngineTests.cs: 11 legacy-resolver tests deleted, 6
  ResolveWithTransition tests kept), 3.2/3.3/3.4 (re-point to canonical
  SetPosition, with TransitionScratchDifferentialTests.cs additionally
  gaining positive IsCommitted assertions after each bitwise comparison so
  the differential proves a placement actually committed, not just that two
  possibly-uncommitted results match), 3.5 (Runtime rename), and 3.6
  (PlayerMovementPlacementTransactionTests.cs rewritten — its xmldoc now
  states plainly that the render-root publish moved to
  RuntimeSetPositionState.cs, but the sticky-release relocation claim was
  false and is retracted; this disposition's coverage loss is the sticky
  release path, not silently absorbed elsewhere).
- Stale `PhysicsEngine.Resolve`/`Resolve` doc citations in CellTransit.cs,
  PlayerMovementController.cs, and HeadlessSessionWorldProjection.cs are
  corrected to name the surviving canonical entry points by symbol
  (SetPosition, AdjustSetPosition/AdjustPosition, ResolveWithTransition)
  rather than fragile line numbers.

Retires AP-1 and AD-1 in docs/architecture/retail-divergence-register.md:
both rows described production zero-delta placement routing remaining on
the legacy resolver pending the Slice 4B2/4B route cutover; that resolver
no longer exists, so the condition each row tracked is now structurally
false rather than merely narrowed. AP-145 (routed through the prior commit)
and this commit's AP-1/AD-1 together bring the section counts to 101 AP / 47
AD active rows.

Builds on the AP-145 fix (previous commit) — this commit's staged tree was
independently rebuilt and its four suites independently rerun on top of
that commit before this commit was created, in addition to the combined
rebuild/rerun below.

Full-solution build: 0 errors (21 pre-existing warnings, all unrelated).
Suite results (combined tree): Core 4270/4271 passed (1 skip; the single
DatSoundCacheTests concurrent-decode-dedup failure is a known load-sensitive
race, confirmed passing standalone and unrelated to this change), Runtime
1176/1176, Headless 86/86, App 4132/4135 (3 skips).

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

src/AcDream.Runtime/Gameplay/PlayerMovementController.cs

@@ -142,8 +142,11 @@ internal enum PlayerMovementControllerPublicationLifecycle
 ///     velocity clamping — all from the decompiled retail client.
 ///   - MotionInterpreter owns the motion state machine: walk/run/jump
 ///     validation, state tracking, speed constants from the retail dat.
-///   - PhysicsEngine.Resolve is still used each frame to snap the player
-///     to terrain/cell floor Z and detect ground contact.
+///   - PhysicsEngine.ResolveWithTransition is still used each frame to snap
+///     the player to terrain/cell floor Z and detect ground contact (C5a,
+///     2026-08-05: the legacy PhysicsEngine.Resolve this note used to name
+///     is deleted, zero production callers; ResolveWithTransition's
+///     sphere-sweep resolver is, and always was, the real per-frame path).
 /// </summary>
 public sealed class PlayerMovementController
 {
@@ -1743,21 +1746,19 @@ public sealed class PlayerMovementController
             _physics.UpdatePlayerCurrCell(newCellId);
     }
 
-    public void SetPosition(Vector3 pos, uint cellId)
-        // #145: tests + legacy callers run in the world==block-local frame (no
-        // streaming center), so the cell-local seed IS the world position. This
-        // makes the carried anchor (body.Position − CellPosition.Origin) == (0,0,0),
-        // identical to the legacy Zero terrain-origin fallback → behaviour unchanged.
-        => SetPosition(pos, cellId, pos);
-
     /// <summary>
-    /// Server-snap / teleport placement. <paramref name="cellLocal"/> is the
-    /// LANDBLOCK-relative position (the wire's local, or world − landblock origin)
-    /// which seeds the body's cell-relative <c>CellPosition</c> WITHOUT any streaming
-    /// center (#145). A teleport is a large jump, so this snaps the cell frame
-    /// directly via <c>SnapToCell</c> rather than delta-syncing through the setter.
+    /// C5a (2026-08-05): this seed exists ONLY to place a controller directly
+    /// in test fixtures. Production placement never calls it — the retail
+    /// server-snap / teleport / enter-world path commits through
+    /// <see cref="PreparePositionForCommit"/> followed by
+    /// <see cref="ArmConstraintLeashAtCommittedPlacement"/> (or, for the
+    /// already-live case, canonical <c>SetPositionCore</c> callers inside
+    /// this class). <paramref name="cellLocal"/> is the LANDBLOCK-relative
+    /// position (the wire's local, or world − landblock origin) which seeds
+    /// the body's cell-relative <c>CellPosition</c> WITHOUT any streaming
+    /// center (#145).
     /// </summary>
-    public void SetPosition(Vector3 pos, uint cellId, Vector3 cellLocal)
+    internal void SeedPlacementForTest(Vector3 pos, uint cellId, Vector3 cellLocal)
     {
         EnsurePublishedForRuntimeOperation();
         SetPositionCore(
@@ -1786,22 +1787,14 @@ public sealed class PlayerMovementController
             publishSharedState: false);
     }
 
-    internal void CommitPreparedPosition()
-    {
-        EnsurePublishedForRuntimeOperation();
-        _physics.UpdatePlayerCurrCell(CellId);
-        PositionManager?.UnStick();
-        // #167 (Campaign P P5): mirrors the SetPositionCore teleport_hook
-        // teardown+rearm below — see that comment for the retail citation.
-        RearmConstraintLeashAtCurrentPosition();
-    }
-
     /// <summary>
     /// C3c-R1: arms the login-entry constraint leash from the Runtime
     /// publication chain. The flip deleted the only login-path caller of
     /// <see cref="RearmConstraintLeashAtCurrentPosition"/> (the App-side
-    /// <see cref="CommitPreparedPosition"/> call in the old
-    /// player-mode-entry commit); the dormant activation's final commit
+    /// <c>CommitPreparedPosition</c> call in the old
+    /// player-mode-entry commit, removed C5a — production placement now
+    /// arms exclusively here and at <see cref="SetPositionCore"/>'s
+    /// teleport_hook teardown+rearm); the dormant activation's final commit
     /// (<c>RuntimeSetPositionState.TryApplyDormantLocalActivationFinalCommit</c>)
     /// is the accepted-position event that replaces it — retail arms at
     /// every accepted-position event (<c>SmartBox::HandleReceivedPosition</c>
@@ -1824,9 +1817,11 @@ public sealed class PlayerMovementController
     /// immediately after <c>TeleportPlayer</c>'s teardown, anchored to the
     /// RECEIVED position (here, the body's just-snapped current position).
     /// Shared by the teleport path (after UnConstrain), the deferred
-    /// player-mode-entry commit path (<see cref="CommitPreparedPosition"/>),
-    /// which never ran UnConstrain because nothing could have armed the
-    /// leash before the controller had a <see cref="PositionManager"/>,
+    /// player-mode-entry commit path (formerly the App-side
+    /// <c>CommitPreparedPosition</c> caller, removed C5a; now
+    /// <see cref="ArmConstraintLeashAtCommittedPlacement"/>'s Runtime-owned
+    /// caller), which never ran UnConstrain because nothing could have armed
+    /// the leash before the controller had a <see cref="PositionManager"/>,
     /// and the C3c first-entry placement commit
     /// (<see cref="ArmConstraintLeashAtCommittedPlacement"/>).
     /// docs/research/2026-07-30-constraint-leash-constants.md §2/§3.2.