wip(standalone): paused by the owner -- hashed maps + inline allocator (no speedup yet), streaming in progress

Hashed TMap/TSet and real TInlineAllocator storage did not move level 0 (72.1 -> 74.1 s, within
noise): the slowness is elsewhere. StreamingWorld.h started (first build hit an int64/uint64
mismatch), library plan drafted (SHARED_CPP_LIBRARY_PLAN.md), before-normal captures saved.
Uncompiled/unmeasured parts: streaming. Resume by forking session 01a0fd2e-3c3b-7050-b4e9-628fdcc4d553.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MmSoF64BbRFmk9C3p1VsBJ

Standalone/SHARED_CPP_LIBRARY_PLAN.md

@@ -0,0 +1,30 @@
+# Shared C++ library plan
+
+## Library contents
+
+Move the deterministic CPU world pipeline into a portable `VoxelForgeCore` library: plain voxel
+and world types, math/noise, density operations and caches, cave and passage fields, strate
+composition, marching cubes, and desired clipmap tile selection. Keep renderer, file loading,
+asset/reflection access, gameplay actors, and task scheduling in the host applications.
+
+## Compatibility boundary
+
+The library should expose standard C++ value types and explicit immutable world inputs. Unreal
+adapters convert `UObject` settings/assets into those inputs and convert mesh results back to
+Unreal types. The standalone loader maps its JSON snapshot into the same inputs. No Unreal headers,
+reflection macros, `UObject`, or host allocator should cross the library boundary.
+
+## Plugin integration
+
+Build the core as one C++20 static library and link it from both the standalone viewer and the
+VoxelForge Unreal module. The plugin keeps ownership of asset loading, worker admission,
+cancellation, collision, game-thread mesh application, and per-frame upload budgets; workers call
+the shared density and meshing API with immutable contexts. The standalone keeps its D3D11 renderer
+and JSON loader and calls the same API.
+
+## Preventing drift before extraction
+
+Until the move lands, keep the standalone copies synchronized from the plugin source with a small
+manifest of shared files and a checked sync script. The script should compare hashes and refuse an
+ambiguous two-sided edit. Run the exported 3,436-sample bitwise parity corpus after every density
+change, then remove the duplicate source only when both hosts build against the shared library.