[codex] Expose small WebGL extensions

[dsafdsaf132]

Summary

• Expose EXT_float_blend and EXT_texture_mirror_clamp_to_edge through getExtension() and getSupportedExtensions().
• Add TypeScript overloads and README extension table entries for the new extensions.
• Add smoke coverage for mirror-clamp texture wrapping and EXT_float_blend additive blending into an RGBA32F framebuffer.

Validation

• npm run build
• npx node-gyp rebuild
• npm run test:webgl2
• npm test
• git diff --check

[chatgpt-codex-connector]

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