- Fix immediate mode (glBegin/glEnd) by using color-per-vertex pattern
- Document Emscripten's requirement for color per vertex in GL_README.md
- Add OpenGL test tab with visual rendering verification
- Test GL_TRIANGLES, GL_QUADS, GL_LINES, GL_LINE_STRIP, GL_LINE_LOOP
- Update wxwidgets submodule with improved context management
Key finding: Emscripten's LEGACY_GL_EMULATION requires glColor*() to be
called before EACH glVertex*() call, not using OpenGL's "current color"
semantic. This is because the stride calculation expects interleaved
vertex data with color per vertex.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
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