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/primitives.rs

@@ -0,0 +1,19 @@
+//! Built-in primitive words for WAFER.
+//!
+//! Primitives are the ~35 words that must be implemented in Rust because
+//! they require direct WASM instructions or host interaction.
+//! Everything else is defined in Forth (loaded from .fth files).
+
+// TODO: Step 6 - Primitive word implementations
+// Each primitive provides:
+// - Its StackEffect (type signature)
+// - Its IR representation (for inlining by the optimizer)
+// - Direct WASM instruction generation
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn placeholder() {
+        // Primitive tests will be added in Step 6
+    }
+}