rename crates/ to engrams/; add el-compiler el package with bootstrap artifact

- crates/ → engrams/ (Rust engrams live here)
- el-compiler/ added: el self-hosting compiler as an el package
  - src/{compiler,lexer,parser,codegen}.el
  - bootstrap/el-compiler.elc (114KB, Rust-compiled seed)
- el.toml Cargo.toml workspace paths updated
- neuron-rs cross-repo path deps fixed (were pointing to products/ instead of foundation/)

el-compiler/src/compiler.el

@@ -0,0 +1,19 @@
+// compiler.el — el self-hosting compiler pipeline
+//
+// Wires lexer -> parser -> codegen into a single compile() function.
+// This is the bootstrap entry point: compiled once by the Rust el-compiler,
+// then self-hosted from that point forward.
+//
+// The returned JSON is an array of bytecode instruction objects matching
+// the serde serialisation format of el-compiler's Bytecode enum.
+
+import "lexer.el"
+import "parser.el"
+import "codegen.el"
+
+// compile — full pipeline: source string -> JSON bytecode string
+fn compile(source: String) -> String {
+    let tokens: [Map<String, Any>] = lex(source)
+    let stmts: [Map<String, Any>] = parse(tokens)
+    codegen(stmts, source)
+}