Fixed

• GLES: MappedAtCreation buffer data silently discarded on Unmap —
  UnmapBuffer only flushed shadow data to GL when BufferUsageMapWrite was set.
  Per WebGPU spec, MappedAtCreation does NOT require MapWrite usage. Buffers
  with Uniform|CopyDst + MappedAtCreation (the standard g3d pattern) had their
  data thrown away — zero MVP matrices, zero vertices, zero indices. Root cause of
  invisible 3D geometry on GLES. (#284)

• GLES: depth/stencil attachment point chosen by format —
  GL_DEPTH_ATTACHMENT for depth-only formats, GL_DEPTH_STENCIL_ATTACHMENT for
  combined. Wrong attachment point caused FBO incomplete (0x506). Rust wgpu-hal
  parity (command.rs:577-580). (#284)

• GLES: depth clear masked by stale pipeline state — ClearDepthCommand now
  calls glDepthMask(true) + glClearDepth(value) before glClear. Prevents
  stale DepthMask(false) from prior pipeline silently masking depth clear. (#284)

• GLES: viewport depth range ignored — SetViewportCommand now calls
  glDepthRange(minDepth, maxDepth). Was ignoring depth range fields entirely.
  Rust wgpu-hal parity (queue.rs:1295-1296). (#284)

Added

• gl.Context.ClearDepth() and gl.Context.DepthRange() wrapper methods for
  both Windows (syscall, double) and Linux (goffi, float32 for GLES).

Changed

• deps: gpucontext v0.22.0 → v0.23.0