feat(render) Campaign FW3.2b-2 step 1: the production leaf adapter

Additive, nothing invokes it yet (the cutover flip is step 2):

- WalkProductionLeafRenderer + RetailPViewPassExecutor.WalkLeaf: the
  walk driver's leaf turns over the SAME executor renderers the packed
  path uses today - DrawWalkSky (the per-slice sky block looped under
  one driver turn), DrawWalkTerrainSlice (the terrain block of
  DrawLandscapeSlice), per-cell shells via EnvCellRenderer,
  DrawWalkPunchFan (PortalDepthMaskRenderer far-Z, +ShellDrawLiftZ
  matching today's DrawPortalDepthWrite until FW3.3 retires it), the
  alpha barrier via FlushLandscapeAlphaFartherThan, and caller-supplied
  clear/seal actions (the renderer owns the pass scope). The cutover
  changes ORDER, never leaf mechanics.
- Punch fans now carry the ACTIVE VIEW INDEX end to end (retail pins
  building_view = Render::portal_view_num @0x0059f3bf for the whole
  two-pass walk; the fan clips by that view's slice planes):
  PortalPassSink.ActiveViewIndex -> IWalkEventSink.OnPunchGeometry ->
  IWalkFrameLeafRenderer.DrawPunchFan.
- The FW3.2b-2 rooting design is recorded in the plan (dual-compute
  split, LookInObject route filtered to dynamics, consumer
  re-pointing, gate list).

Suites: full Release build 0 warnings; Walk lane green; hermetic green.

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

src/AcDream.App/Rendering/RetailPViewPassExecutor.cs

@@ -114,7 +114,7 @@ internal interface IRenderFrameEntityPassExecutor
 /// is written once; the four places it touches graphics state directly are owned
 /// by <see cref="IWorldPassSurface"/>.
 /// </summary>
-internal sealed class RetailPViewPassExecutor :
+internal sealed partial class RetailPViewPassExecutor :
     IRetailPViewPassExecutor,
     IRenderFrameEntityPassExecutor,
     IOutdoorSceneParticleOwnerSource