feat(render) Campaign FW3.2b-1: the walk frame driver

WalkFrameDriver executes one full static-content frame from the walk's
turns so GPU command-buffer order equals retail's walk order. One rule
does the interleaving: the accumulated OrderedDrawStream flushes
through SubmitOrderedStream immediately before EVERY non-stream draw
(sky, terrain slice, cell shell, punch fan, alpha barrier).

Turn script, all decomp-cited and two of them corrected in review:
- Interior flood: per cell IN FLOOD ORDER, shell first then contents
  (PView::DrawCells @0x005a4840: DrawEnvCell @0x005a4abe precedes
  DrawObjCellForDummies @0x005a4b0d).
- Landscape: sky once, terrain per active slice, then blocks
  far-to-near; per cell the building turn precedes the cell's outdoor
  statics (DrawSortCell @0x0059f140).
- Building (DrawBuilding @0x0059f2a0): the BLD probe event stays at
  entry, but the ENTIRE body - alpha barrier, portal passes, shell -
  sits inside retail's gfxobj[deg_level]!=0 gate @0x0059f2d3, and the
  order is FlushAlphaList @0x0059f30b -> the two-pass punch/look-in
  walk -> THEN the shell draw @0x0059f345. The driver review caught
  both the missing gate and a shell-before-punch inversion; fixed
  with the addresses cited.

Walk seam: three additive default-implemented IWalkEventSink hooks
(OnLandscapeCellTurn / OnBuildingTurn / OnBuildingShellTurn /
OnPunchGeometry) - every existing sink and all FW1 conformance
fixtures unchanged. WalkLandBlock gains LandblockId for the cell-id
encoding. Leaf draws go through IWalkFrameLeafRenderer so FW3.2b-2
wires the real renderers and the referee suite runs on fakes +
RecordingGpuDevice.

Flagged for FW3.2b-2/FW4 adjudication (documented in code):
FlushFartherThan(building distance) vs retail flush-all
FlushAlphaList(0f); terrain-before-statics within the landscape turn.

Suites: full Release build 0 warnings; Walk lane 200/1 skip;
InstalledDat Walk conformance 40/1 untouched; hermetic 6,752/0.

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

src/AcDream.App/Rendering/Walk/WalkEvents.cs

@@ -51,8 +51,78 @@ public readonly record struct WalkEvent(
 /// <summary>
 /// The sink a walk emits into. FW1 conformance tests collect events; FW2's
 /// production sink will additionally receive the ordered draw stream.
+///
+/// <para>Campaign FW3.2b-1 additive seam: <see cref="RetailFrameWalk"/> also
+/// calls the four richer, default-no-op members below at turns the
+/// vocabulary-only <see cref="WalkEvent"/> stream cannot express (a visited
+/// landscape cell with no building emits no <see cref="WalkEvent"/> at all;
+/// <see cref="WalkEventKind.Building"/> carries only a cell id, not the
+/// <see cref="WalkBuilding"/> reference a driver needs to look up shell
+/// content, degrade state, or world transform; and punches are not part of
+/// the FW1 conformance vocabulary at all — the oracle traces do not log
+/// them). Every FW1/FW2 sink that only implements <see cref="Emit"/>
+/// continues to compile and behave identically — these are C# default
+/// interface members, never called by any pre-FW3.2b-1 code path.</para>
 /// </summary>
 public interface IWalkEventSink
 {
     void Emit(in WalkEvent walkEvent);
+
+    /// <summary>
+    /// Fires once per visited landscape cell, AFTER that cell's building
+    /// turn (if any) — <c>RenderDeviceD3D::DrawSortCell</c> @0x0059f140
+    /// calls <c>DrawBuilding(building)</c> first, then
+    /// <c>DrawObjCell(cell)</c> UNCONDITIONALLY (decomp-confirmed
+    /// 2026-08-30). <paramref name="cellId"/> follows retail's outdoor cell
+    /// encoding — <c>(landblockId &amp; 0xFFFF0000) | (cellIndex + 1)</c> —
+    /// the same convention <see cref="WalkLandscapeAssembler.BuildSlot"/>
+    /// and <see cref="WalkProductionFrameContext.SetViewer"/> +
+    /// <see cref="WalkLandscapeAssembler.SetViewer"/> already use. Default
+    /// no-op.
+    /// </summary>
+    void OnLandscapeCellTurn(uint cellId) { }
+
+    /// <summary>
+    /// Fires at <see cref="RetailFrameWalk.DrawBuilding"/> once retail's own
+    /// gate has passed — <c>RenderDeviceD3D::DrawBuilding</c> @0x0059f2a0
+    /// wraps its ENTIRE body (the alpha barrier, the portal pass, the shell
+    /// draw) in <c>if (part-&gt;gfxobj[part-&gt;deg_level] != 0)</c>
+    /// @0x0059f2d3 — a degraded-out slot draws NOTHING beyond the
+    /// unconditional <see cref="WalkEventKind.Building"/> <see cref="Emit"/>
+    /// call. <see cref="WalkBuilding.HasGeometry"/> and a non-null
+    /// <see cref="WalkBuilding.SelectDrawingBsp"/> result together model that
+    /// one gate, so this hook fires only after both have passed. This is the
+    /// ALPHA BARRIER turn (<c>D3DPolyRender::FlushAlphaList(0f)</c>
+    /// @0x0059f30b) — retail's own order runs it BEFORE the portal pass
+    /// (<c>CPhysicsPart::Draw(parts, 1)</c>), which in turn runs BEFORE the
+    /// shell draw (<c>CPhysicsPart::Draw(parts, 0)</c> — see
+    /// <see cref="OnBuildingShellTurn"/>, fired separately, after the portal
+    /// pass completes). Default no-op.
+    /// </summary>
+    void OnBuildingTurn(WalkBuilding building) { }
+
+    /// <summary>
+    /// Fires at the END of <see cref="RetailFrameWalk.DrawBuilding"/>, after
+    /// its two-pass portal walk (punches + look-ins, across every active
+    /// view) has fully completed — <c>CPhysicsPart::Draw(parts, 0)</c>
+    /// @0x0059f331, retail's plain-mesh draw of the building's own shell,
+    /// which runs strictly AFTER <c>CPhysicsPart::Draw(parts, 1)</c> (the
+    /// portal flavor) per the decomp sequence at @0x0059f30b–0x0059f345. Only
+    /// fires when <see cref="OnBuildingTurn"/> also fired (same gate; see its
+    /// doc comment) — a degraded-out slot reaches neither. Default no-op.
+    /// </summary>
+    void OnBuildingShellTurn(WalkBuilding building) { }
+
+    /// <summary>
+    /// Fires when the two-pass portal machinery
+    /// (<see cref="WalkBuildingPortals"/>) would draw a far-Z punch fan
+    /// (<c>DrawPortalPolyInternal</c> @0x0059bc90, pass 1) — carries the
+    /// owning building and the polygon in BUILDING-LOCAL space (as stored on
+    /// the emitted <see cref="WalkPortalRef"/>) so a driver can resolve the
+    /// world transform itself. The FW1 oracle traces never log punches
+    /// (<see cref="RetailFrameWalk"/>'s internal <c>PortalPassSink.OnPunch</c>
+    /// stayed a no-op through FW1/FW2 for exactly that reason). Default
+    /// no-op.
+    /// </summary>
+    void OnPunchGeometry(WalkBuilding building, WalkPolygon polygon) { }
 }