MeshCue 1.3.1

STEP and STL now stand upright. Neither format records which way is up, and
MeshCue drew both as if +Y were, so anything modelled Z-up -- every build123d,
CadQuery or OCCT part, and every STL a slicer has touched -- lay on its side.
Both are now drawn with +Z up, -Y towards the reviewer and +X to the right. GLB
is unchanged: glTF defines +Y up itself. There is no setting for it. A model
built another way should be rotated before it is published, and
AGENT-INTERFACE.md now says so. Marks are unaffected: pins and region extents
stay in the published file's own coordinates.

If you have been rotating STL files to Y-up so that they would stand in
MeshCue, stop: they will now lie down.

The colours a STEP declares on its solids now reach the page, and so does its
transparency. The bundled tessellator reads a colour only where it is filed
against a whole part, so a part made of several solids -- a coloured compound
in build123d, a multi-body part in CAD -- came out grey, and nothing was ever
drawn translucent. MeshCue now reads the styles from the file itself, and gives
them only to meshes it can check against the solids they came from. Across
1,024 real STEP files, meshes with a colour went from 6,601 to 7,896, 465
gained their opacity, and no colour the tessellator had read changed. Meshes
made by 1.3.0 are kept as they are, because marks are anchored to them:
publish a STEP again to see its colours.

Looking straight down or up from the view cube no longer changes how the right
button turns the model. It used to switch the camera's up vector, which the
orbit only reads once, so a sideways drag afterwards hardly turned anything
until a side face or home put it back.

Publishing the same STEP again reuses its mesh instead of tessellating it
again, and a STEP no longer needs precheck: open measures it while importing
and refuses it the same way, so a round tessellates once instead of twice. A
STEP is labelled in millimetres, which its mesh always is.

Also:

• A converter that crashes says what it crashed on.
• A package with a part missing says which part, instead of a bare ENOENT.
• inspect reports the build that is running, not the one on disk.
• A project whose folder was deleted leaves the registry, instead of being
  warned about at every Gateway start and stop.
• A clone runs from itself: samples go to tmp/samples, published copies to
  runtime/models, and nothing is written two directories above it.
• three-mesh-bvh 0.9.15, zod 4.6.5, prettier 3.9.8. three.js stays at 0.180.

This release is commit 106e6c9.