0.34.0

• feat(glyphs): add directional lighting to TexturedGlobeGlyph (#320)
• Add a sun unit vector and an ambient floor so the globe can be lit from a
  direction, shading a lambertian day/night terminator instead of reading as
  evenly illuminated. sun=None (the default) renders byte-identical to 0.33.0.
• • Accept sun/ambient on init and override per call on draw/animate
    (mirroring spin, via an inherit sentinel so sun=None can disable lighting
    for one call); sun is world-space (+z up/north, +x toward the viewer at
    spin=0), auto-normalized to unit length; ambient must be in [0, 1].
• Apply lighting per frame from the already-rotated vertices (one dot product
  over the mesh, whose unit-sphere positions are the surface normals), scaling
  a copy of the cached facecolors by
  ambient + (1 - ambient) * clip(dot(normal, sun), 0, 1). The facecolors cache
  is never mutated and the texture is never re-sampled, so the
  sample-once/rotate-per-frame contract holds and a fixed sun sweeps the
  terminator as the globe spins; alpha is preserved.
• Validate sun/ambient eagerly on both draw and animate; reject non-1-D or
  zero sun vectors and out-of-range ambient.
• Add lighting tests (byte-identical sun=None, terminator + ambient floor,
  lit fraction tracks spin, cache untouched, world-space sun under tilt,
  validation) and a reference-doc example.
• Closes #319