v0.3.7

A thirteenth review, six findings. The worst is mine from 0.3.6, and it is the
same defect that release's own comment quotes while introducing it.

Data destruction

• mergeDistance: 0 destroyed geometry on a scaled object and reported
  success. 0.3.6 special-cased the zero branch as a 1e-6 constant in LOCAL
  units with no divisor, while both other branches divided. The world radius was
  therefore 1e-6 x divisor, and the branch below skips whenever the request
  is narrower than that — so asking for zero merging applied a strictly wider
  repair than asking for a small positive one. Two files with byte-identical
  world geometry went to 100 and 0 triangles; a partial case lost 98% (102
  triangles to 2) with readyToTexture: true and the skip counter reading zero.

  The test could not see it: hardcoded to one merge distance, against a fixture
  at scale [1,1,1] — divisor 1 is the single value at which it is invisible.
  Fixed by deleting the special case rather than patching it, so every path runs
  the one divisor rule and is monotonic by construction.

Wrong verdicts, at severity error

• sceneGraphFallback asked "does the default scene draw nothing?" rather
  than "does any scene reference a mesh?". A Blender export whose default scene
  holds only a camera, geometry in a second scene, is ordinary — and it took the
  mesh-library fallback, counting undrawn meshes as drawn. That restored both
  defects the narrowing exists to prevent. It worked only when the default scene
  happened to be non-empty, which is exactly what its test covered.
• Materials, textures and the PBR summary stayed file-scoped while geometry
  was narrowed, so the two halves of one report described two different files.
  A normal map bound only by an undrawn collision proxy failed
  tangents_for_normal_map on a model that correctly needs no tangents; a
  base-colour texture on an undrawn LOD satisfied base_color_texture for a
  drawn mesh that has none. Textures now derive from the drawn materials.

Values that reached no caller

• The batch dropped the new dissolve-skip flag — the fourth consecutive
  release in which that seam lost a flag the layer below computed.
• textureFailures on the unreadable-container path was pinned by nothing;
  deleting it left the whole suite green. Now covered end-to-end through a real
  HTTPS server, because the download layer refuses non-HTTPS URLs outright.
• The four inspection fields were pinned only at the helper. ok() takes
  unknown, so the compiler guards summarizer-to-interface and nothing guards
  interface-to-client — the exact hop where four fields have now been lost. A
  mutant destructuring them out on the way to the response compiles cleanly;
  only a test through a real MCP client can see it.
• A texture with no image data was silently skipped, vanishing from
  textureCount with nothing said.

Verification

Every fix reverted and observed to fail, each mutant confirmed to compile and
to have actually applied. One near-miss worth recording: a field assignment
landed while its interface declaration silently did not, and the tests passed
while tsc failed, because vitest does not typecheck. The rule that keeps
catching this remains: put the field on the output type first.