WASM compilation target and multi-language bindings

[ds1sqe]

Context

Part of the Rust core epic (#95, Phase 3). The Rust core currently compiles only as a PyO3 extension. The RFC envisions the same core running in browsers (WASM), edge functions, and other language runtimes via C FFI.

Goal

Compile the Rust core to WASM and provide C FFI for language-agnostic bindings, enabling TypeSchema, ValidationEngine, and QueryCompiler to run outside Python.

Scope

WASM target

• Conditional compilation: #[cfg(target_arch = "wasm32")] guards for PyO3-free builds
• wasm-bindgen or wasm-pack setup for browser/Node.js
• Expose ValidationEngine, QueryCompiler, TypeSchema via JS-friendly API
• npm package for browser/Node.js consumption
• Bundle size optimization (tree-shaking unused features)

C FFI

• cbindgen header generation
• C-compatible API: type_bridge_* function prefix, opaque handles, error codes
• Memory management: caller-owned strings, type_bridge_free_* functions

Multi-language bindings (stretch)

• Node.js via napi-rs or WASM
• Go via CGo + C FFI
• Example usage in each target language

Build & CI

• wasm-pack build in CI
• WASM artifact upload alongside Python wheels
• Feature flags: features = ["python", "wasm", "ffi"]

Dependencies

• Core API stabilization (all Phase 1-2 issues should be settled)

Acceptance criteria

• wasm-pack build produces a working .wasm + JS glue
• A minimal JS test validates a type name and compiles a query from the browser
• C header is generated and a minimal C program links against the library
• No PyO3 dependency in the WASM/FFI build