Add CI workflow #2

Motivation

A comprehensive CI pipeline is needed to validate every PR. This should cover linting, building across all target platforms, testing, and coverage reporting.

Tasks

• Create ci.yml with the following jobs:
  • Lint: Biome check, TypeScript typecheck, publint, verify generated bindings
  • Audit: pnpm audit + cargo-deny
  • Rust Lint: cargo fmt --check + cargo clippy
  • Rust Test: cargo test
  • Build: Cross-compile for all 9 napi-rs targets (2 macOS, 4 Linux, 2 Windows, 1 WASM)
  • Test: Run Vitest on 3 Node versions × 3 OSes
  • Coverage: Rust (cargo-llvm-cov) + JS (vitest --coverage), upload to Codecov
  • WASM Tests: Browser (Playwright), Bun, Deno
• Verify all jobs pass on the initial codebase

Dependencies

• Set up napi-rs build pipeline #1 (build pipeline must be working first)

Acceptance Criteria

• All CI jobs pass on a PR to develop
• Coverage reports appear on Codecov
• Build artifacts are produced for all 9 targets