Initial commit: WAFER (WebAssembly Forth Engine in Rust)

Optimizing Forth 2012 compiler targeting WebAssembly with IR-based
compilation pipeline, multi-typed stack inference, subroutine threading,
and JIT/consolidation modes. Rust kernel with ~35 primitives and Forth
standard library for core/core-ext word sets.

crates/core/src/codegen.rs

@@ -0,0 +1,21 @@
+//! WASM code generation from IR.
+//!
+//! Translates optimized IR into WASM bytecode using the `wasm-encoder` crate.
+//! Supports two modes:
+//! - **Typed mode**: when type inference succeeds, values stay in WASM locals
+//! - **Fallback mode**: load/store against stack pointer globals in linear memory
+
+// TODO: Step 5 - Full codegen implementation
+// - IR -> WASM function body translation
+// - Single-word module generation (JIT mode)
+// - Multi-word module generation (AOT/consolidation mode)
+// - Typed vs fallback mode selection
+// - Function table management
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn placeholder() {
+        // Codegen tests will be added in Step 5
+    }
+}