Function parseBinaryMeshBatch

Parses a binary mesh batch blob in the SLVA wire format.

The blob layout is:

  [4]  magic        = "SLVA" (0x53 0x4C 0x56 0x41)
  [4]  version      = uint32 (currently 1)
  [4]  metadataLen  = uint32 byte length of UTF-8 metadata JSON
  [N]  metadata     = UTF-8 JSON (materials, groups, sourceComponentId, ...)
  [4]  flags        = uint32 (bit 0: 0 = int16 quantized, 1 = float32 raw)
  [24] origin       = 3 x float64
  [24] scale        = 3 x float64 (step per int16 unit; identity for float32)
  [4]  vertexCount  = uint32 number of vertices (positions = vertexCount * 3 components)
  [V]  vertices     = int16[vertexCount*3] OR float32[vertexCount*3]
  [4]  indexCount   = uint32 number of indices
  [I]  indices      = uint32[indexCount]
Copy

For int16 vertices: world position = origin + (q + 32767) * scale. This matches Three.js BufferAttribute(arr, 3, true) (normalized: true) semantics when the per-mesh transform encodes origin + scale.

For float32: origin = (0, 0, 0), scale = (1, 1, 1), vertices are raw world positions.