feat(render): indoor render WORKS — terminating portal flood + every-cell seal + look-in FPS

Checkpoint of the unified retail-faithful indoor render. The two-week HANG/grey is fixed and the
interior seals (live-verified by the user). Commits the session render-rewrite foundation together
with the fixes that made it functional.

- HANG fix: PortalVisibilityBuilder.Build portal flood did not terminate (the faithful ProjectToClip
  near-side clip drifts per round, defeating the CellView dedup; the BFS had no bound after U.2a removed
  MaxReprocessPerCell). Fix = drift-tolerant snapped/canonical CellView.Add dedup (PortalView.cs) plus
  restored MaxReprocessPerCell=16 bounded re-enqueue (PortalVisibilityBuilder.cs). Re-enqueue is kept
  (load-bearing for late-slice propagation, Build_ViewGrowthAfterDoneCell_PropagatesNewSlicesToExit);
  only its count is capped. CellViewDedupTests added.
- Seal (DrawCells Task 2): RetailPViewRenderer.DrawEnvCellShells draws EVERY visible cell via
  IndoorDrawPlan.ShellPass (was gated on the ClipFrameAssembler slot filter, leaving slot-less cells grey).
- Look-in FPS: GameWindow exterior look-in candidates limited to the player landblock +-1 (was all ~81
  loaded LBs iterated every outdoor frame). No behaviour change (far cells were >48m, already culled).

Remaining dominant issue = the FLAP at transitions: viewer-cell metastability (render roots at the
camera-eye cell, which oscillates outdoor-indoor as the 3rd-person boom drifts across the doorway,
confirmed in render-sig). SEPARATE fix, NOT the DrawCells port. Full handoff + flap fix plan + tracked
follow-ups (#78 terrain, look-in-from-inside, look-in FPS, L-spotlight):
docs/research/2026-06-07-indoor-render-session-handoff.md.

Baselines: build 0 err; App.Tests 210/210; Core.Tests 1331 pass / 4 fail (pre-existing) / 1 skip.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/AcDream.Core.Tests/Rendering/RenderingDiagnosticsTests.cs

@@ -96,40 +96,40 @@ public sealed class RenderingDiagnosticsTests
     // PLAYER's cell, 0x451e80), NOT the camera cell. acdream previously branched on the
     // camera cell, so a chase camera lagging in a doorway while the player was already
     // outside took the DrawInside path and degenerated to a grey world + entities showing
-    // through walls. These pin the player-keyed branch (DrawInside root stays the viewer cell).
+    // through walls. These pin the player-keyed branch and loaded player-root requirement.
 
     [Fact]
     public void ShouldRenderIndoor_PlayerOutside_CameraInside_ReturnsFalse()
     {
         // THE doorway-grey regression: the player stepped onto a landcell (0x...0031) but the
         // chase camera still resolves an interior EnvCell. Branch on the PLAYER → outdoor.
-        Assert.False(RenderingDiagnostics.ShouldRenderIndoor(playerCellId: 0xA9B40031u, viewerCellResolved: true));
+        Assert.False(RenderingDiagnostics.ShouldRenderIndoor(playerCellId: 0xA9B40031u, renderRootResolved: true));
     }
 
     [Fact]
     public void ShouldRenderIndoor_PlayerInside_CameraInside_ReturnsTrue()
     {
-        Assert.True(RenderingDiagnostics.ShouldRenderIndoor(playerCellId: 0xA9B40171u, viewerCellResolved: true));
+        Assert.True(RenderingDiagnostics.ShouldRenderIndoor(playerCellId: 0xA9B40171u, renderRootResolved: true));
     }
 
     [Fact]
-    public void ShouldRenderIndoor_PlayerInside_NoViewerCell_ReturnsFalse()
+    public void ShouldRenderIndoor_PlayerInside_RootNotLoaded_ReturnsFalse()
     {
         // Opposite lag (camera pulled outside while the player is inside): no viewer cell to
         // root DrawInside at → outdoor. Defensive; matches prior null-CameraCell behavior.
-        Assert.False(RenderingDiagnostics.ShouldRenderIndoor(playerCellId: 0xA9B40171u, viewerCellResolved: false));
+        Assert.False(RenderingDiagnostics.ShouldRenderIndoor(playerCellId: 0xA9B40171u, renderRootResolved: false));
     }
 
     [Fact]
     public void ShouldRenderIndoor_PlayerOutside_CameraOutside_ReturnsFalse()
     {
-        Assert.False(RenderingDiagnostics.ShouldRenderIndoor(playerCellId: 0xA9B40031u, viewerCellResolved: false));
+        Assert.False(RenderingDiagnostics.ShouldRenderIndoor(playerCellId: 0xA9B40031u, renderRootResolved: false));
     }
 
     [Fact]
     public void ShouldRenderIndoor_UnknownPlayerCell_TreatedAsOutside_ReturnsFalse()
     {
         // playerCellId == 0 (unresolved) → treat as outside (safe default: outdoor render).
-        Assert.False(RenderingDiagnostics.ShouldRenderIndoor(playerCellId: 0u, viewerCellResolved: true));
+        Assert.False(RenderingDiagnostics.ShouldRenderIndoor(playerCellId: 0u, renderRootResolved: true));
     }
 }