perf: replace the React playground with vanilla TypeScript

[aomona]

Summary

• replace the React playground runtime with vanilla TypeScript and static HTML
• preserve the visible controls, labels, initial values, layout, WebGL behavior, context recovery, and reduced-motion handling
• remove ReactDOM, the Vite React plugin, and their playground-only transitive dependencies

Verification

• npm run format:check
• npm run lint
• npm run typecheck
• npm test (16 tests on the stacked branch)
• npm run build:playground
• browser checks for preset changes, ranges, seed clamping, reset, and ready state
• same-tab visual comparison: normalized MAE 0.0291%

Size

• playground JavaScript: 208.58 kB to 14.70 kB
• playground JavaScript gzip: 65.54 kB to 5.58 kB

Dependency

This PR is intentionally stacked on codex/package-boundaries so the final dependency metadata merges without conflicts. After the package PR lands, this PR can be retargeted to main.