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/)

engrams/el-manifest/src/lib.rs

@@ -0,0 +1,28 @@
+//! el-manifest — `el.toml` project manifest parser.
+//!
+//! Every Engram project has an `el.toml` at its root. This crate defines the
+//! manifest data model and parses it from TOML text.
+//!
+//! # Quick start
+//! ```rust
+//! use el_manifest::Manifest;
+//!
+//! let toml = r#"
+//! [package]
+//! name = "my-service"
+//! version = "0.1.0"
+//! edition = "2026"
+//! "#;
+//! let manifest = Manifest::parse(toml).unwrap();
+//! assert_eq!(manifest.package.name, "my-service");
+//! ```
+
+mod error;
+mod manifest;
+mod parse;
+
+pub use error::{ManifestError, ManifestResult};
+pub use manifest::{
+    BuildConfig, BuildTarget, CrossConfig, CrossTarget, Dependency, Manifest, NativeTarget,
+    PackageInfo, SealKeySource,
+};