Implement core Forth runtime: dictionary, codegen, outer interpreter, REPL

- Dictionary: linked-list word headers in simulated linear memory with
  create/find/reveal, case-insensitive lookup, IMMEDIATE flag support
- WASM codegen: IR-to-WASM translation via wasm-encoder with full
  validation; all stack, arithmetic, comparison, logic, memory, control
  flow, and return stack operations; wasmtime execution tests
- Outer interpreter: tokenizer, number parsing (decimal/$hex/#dec/%bin),
  interpret/compile dispatch, control structures (IF/ELSE/THEN,
  BEGIN/UNTIL, BEGIN/WHILE/REPEAT), RECURSE, comments, string output
- 40+ primitive words registered via JIT-compiled WASM modules linked
  to shared memory/globals/table
- Interactive REPL with rustyline, piped input, and file execution
- 145 tests passing across dictionary, codegen, and runtime

crates/core/Cargo.toml

@@ -8,10 +8,10 @@ license.workspace = true
 [dependencies]
 wasm-encoder = { workspace = true }
 wasmparser = { workspace = true }
+wasmtime = { workspace = true }
 anyhow = { workspace = true }
 thiserror = { workspace = true }
 
 [dev-dependencies]
 proptest = { workspace = true }
 insta = { workspace = true }
-wasmtime = { workspace = true }