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-test/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "el-test"
+description = "Engram language unified testing framework — unit and e2e same syntax, seed-based graph testing"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+
+[dependencies]
+el-lexer    = { workspace = true }
+el-parser   = { workspace = true }
+el-types    = { workspace = true }
+el-compiler = { workspace = true }
+serde       = { workspace = true }
+serde_json  = { workspace = true }
+thiserror   = { workspace = true }