a3d 0.9.4

[0.9.4] - 2026-10-05

A lighting fix on the binned path, and a tutorial. A skinned model renders
exactly as it did on 0.9.3; a model whose parts are placed by node transforms
is lit as the unbinned path always lit it.

Fixed

• A container whose parts are placed by node transforms was lit wrongly by
  a3d::Viewer, and by anything else on the binned path.
  SceneRuntime::drawDrawableTile() sets the material and the shading model
  before handing the backend a ProjectedBatch, but never set the MODEL
  MATRIX. Positions do not need it - the binner has already projected them -
  but lighting does: the backend carries the light into the mesh's own space
  using that matrix, so without it every rotated part was lit as though it had
  not been rotated.

  Invisible on a SKINNED model, which is why it survived: skinning has already
  put the normals in world space and _modelMatrix() hands back identity for
  one, so Fox and CesiumMan - both skinned, and both of the shipped fixtures -
  render byte for byte identically before and after this change. Every
  published measurement stands.

  Measured on a 7-part node-animated car at 400x400 with the light a3d
  defaults to: mean red across the lit pixels went from 5.7/31 to 13.2/31, and
  13.2 is what the unbinned path (SceneRuntime::draw(), which a3d_view
  uses) produced from the same light all along. The two paths are meant to
  agree, and the comment above _prepare() says so.

  Viewer::_drawMeshTile() had this right for the array path and carries the
  comment explaining why; the container path is now the same.

Added

• examples/ESP-IDF/Tutorial_01: six lessons from an empty screen to an
  endless top-down race track, selected by one #define. Splits into a board
  half and an a3d half that names no vendor header, so the lessons compile on
  a host - which is how its README's pictures were made.

  It is landscape on a panel that scans portrait, which a MIPI-DSI video
  panel cannot be asked to do: the DPI peripheral scans the framebuffer out in
  hardware and esp_lcd_panel_swap_xy() is not implemented for it. So the
  example draws 1280x800 and rotates each strip into the 800x1280 panel in its
  own a3d::Display wrapper - which needs no change to a3d at all, because a
  Display is a size and a blit and nothing above it can tell that the blit
  happens to turn the pixels. The transpose is checked pixel for pixel against
  an independent rotation, both directions, with tile heights that do and do
  not divide the screen, and the example has been flashed and run on the
  Waveshare ESP32-P4-Nano with the 10.1" panel it is written for, where the
  full scene runs at 14 fps.

Changed

• idf_component.yml also excludes examples/ESP-IDF/Tutorial_01/docs/**,
  the tutorial's 1.1 MB of README pictures, which its README already serves
  from raw.githubusercontent.com. The tutorial builds without them.
• The README's install examples and a3d_export.py --project pin v0.9.4.