ci: close four gaps (wasm-opt, audit, coverage, parity) - #267

Overview

Closes four independent CI weaknesses in .github/workflows/ci.yml by adding or hardening jobs for WASM optimization, dependency scanning, coverage, and SDK error-code parity.

Related Issue

Closes #262

Changes

[FIX] WASM optimization

• [MODIFY] scripts/build_wasm.sh
  • Fail with exit 1 if wasm-opt is missing when optimization is expected (no more silent skip).
  • Print optimized artifact sizes at the end of the build.
• [MODIFY] .github/workflows/ci.yml
  • Install binaryen in the build job so wasm-opt is available.
  • Add a step that prints optimized WASM sizes to the job summary.

[ADD] Dependency scanning

• [ADD] .github/workflows/ci.yml — new audit job
  • Installs cargo-audit and runs cargo audit.
  • Fails CI on known advisories.

[ADD] Coverage reporting

• [ADD] .github/workflows/ci.yml — new coverage job
  • Installs cargo-tarpaulin and runs it across the workspace.
  • Reports total coverage to stdout.

[ADD] SDK error code parity check

• [ADD] scripts/check_error_parity.py
  • Compares discriminants in contracts/marketx/src/errors.rs against keys in sdk/error-codes.ts.
  • Fails CI if a mismatch exists in either direction.
• [MODIFY] .github/workflows/ci.yml — new sdk-parity job
  • Runs the parity script and fails on mismatch.

[MODIFY] Documentation

• [MODIFY] CONTRIBUTING.md
  • Documents how to run cargo audit, cargo tarpaulin, and the parity check locally.
  • Adds a "Local CI Workflow" section that reproduces all checks before pushing.

Verification Results

cargo fmt --all -- --check       ✅ passed
cargo clippy --all-targets -- -D warnings  ✅ passed (zero warnings)
cargo test                       ✅ passed (123 unit + 2 integration tests)
python3 scripts/check_error_parity.py  ✅ passed

Acceptance Criteria