Fix cross-browser ProveKit WASM demo and gate it in CI

[dcbuild3r]

Summary

• replace the Firefox-breaking Verity/import-map runtime with the first-party @worldcoin/provekit browser SDK
• regenerate PKP 2.0 / PKV 2.1 artifacts with the package release toolchain and bundle the Safari-safe scalar fallback
• add real proof-generation and verification E2E coverage for Chromium, Firefox, and WebKit
• run CI on every pushed branch and install a local pre-push gate via Bun
• remove obsolete vendored Noir/Verity runtime files

Verification

• bun run format:check
• bun run lint
• bun run check
• bun run test
• bun run build
• bun run test:e2e (10 passed, 2 skipped; real proof verified in all three browser engines)

Known baseline

• bun run lhci still reports the existing homepage performance score of 0.82 against the repository threshold of 0.98; other local gates pass.