Covers:
- What antibot_wasm.js is and why it is not in the repo
- How wasm-pack compiles wasm/src/ and what wasm/pkg/ contains
- Step-by-step build (rustup target, wasm-pack install, build, mv to frontend/pkg)
- How heartbeat.js loads and initialises the module via await init()
- MIME type requirements for serving .wasm files
- .gitignore rationale for wasm/pkg/ and frontend/pkg/
- Troubleshooting (missing target, wasm-opt, 404, empty string returns)
