Optimize WebGL frame transforms

[aomona]

Summary

• Move per-frame motion trig and transform values from fragment shader work into JS-computed uniforms
• Keep the public API and visual behavior unchanged while reducing per-pixel shader work
• Add shader source assertions covering the uniform-based transform path

Test Plan

• npm run typecheck
• npm run build
• npm test
• npm run build:playground
• npm run lint
• npm run format:check

[Copilot]

Pull request overview

This PR optimizes the WebGL fragment shader by moving per-frame trigonometry and transform math (rotation/zoom/travel) out of per-pixel shader execution and into CPU-computed uniforms, aiming to reduce fragment shader work without changing the public API or visual output.

Changes:

• Replace time/swirl/zoom/rotate/travel-driven per-pixel trig in the fragment shader with precomputed per-frame uniforms (u_frameRotationSin, u_frameRotationCos, u_frameScale, u_frameTravel).
• Update the WebGL renderer to compute and upload the new per-frame uniforms each render.
• Add regression assertions in tests to ensure the uniform-based transform path exists and per-pixel trig patterns are absent from the built shader source.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
tests/library.test.mjs	Adds build-output assertions to validate the uniform-based transform path and avoid per-pixel motion trig in the fragment shader.
src/webgl.ts	Moves per-frame trig/transform computation into JS and updates the fragment shader + uniform plumbing accordingly.

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