fix(render): DynamicLast admits only the walk''s own root flood

The [dyn-route] trace pinned the through-wall remote player (visible
from 0xF4180101 AND outdoors while parented at 0xF4180112 - a cell
with no retail sightline chain from either): the legacy visibility
builder invents cross-building cell views at the cathedral (REAL
3-5-plane cones for 0x112, not the zero-plane trapdoor), the viewcone
admits his sphere, and he rides the last dynamics pass - post-clear on
interior roots (walls'' depth wiped) and post-world outdoors.

The stage-set split (synthesis plan step 4): an interior-parented
dynamic may ride DynamicLast ONLY when its parent cell is in THE
WALK''S OWN ROOT FLOOD (oracle-trace-conformant; retail draws look-in
occupants inside the landscape stage through the composed portal
chain, and unreachable cells'' occupants not at all). The frame
product''s build input gains RootFloodCells (the driver''s
InteriorFloodCells as a per-frame set); non-walk/diagnostic frames and
the comparison wrapper keep the legacy drawableCells meaning. The
[dyn-route] probe logs the new rootflood-excluded state.

Hermetic 6,762/0; InstalledDat walk conformance 40/1.

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

tests/AcDream.App.Tests/Rendering/RenderScenePViewFrameProductTests.cs

@@ -162,7 +162,8 @@ public sealed class RenderScenePViewFrameProductTests
                 [Cell],
                 EmptyCellSource.Instance,
                 [],
-                RootIsOutdoor: true);
+                RootIsOutdoor: true,
+                RootFloodCells: new HashSet<uint> { Cell });
             builder.Build(exchange, frameSequence, in input);
         }
     }