fix cross-repo path deps; remove el compiler from neuron-lang/

- neuron-runtime, neuron-store, neuron-migrate: fix path deps
  (products/engram/ → foundation/engram/engrams/, products/el/ → foundation/el/engrams/)
- neuron-rs workspace: fix axon-events/axon-protocol paths
  (../../../platform/ → ../../platform/, paths were off by one level)
- neuron-lang/compiler/ removed (el self-hosting compiler now lives in foundation/el/el-compiler/)

crates/neuron-api/src/main.rs

@@ -34,6 +34,10 @@ async fn main() {
     let state = AppState::new(&db_path, api_key).expect("failed to initialize app state");
     let state = Arc::new(state);
 
+    // Run on_startup hooks — each .el module with `fn on_startup` gets its
+    // own background thread. The loop timing and logic live entirely in Engram.
+    state.runtime.run_startup_hooks();
+
     let app = routes::build_router(state);
 
     let listener = tokio::net::TcpListener::bind(&bind)