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-protocol/src/lib.rs

@@ -1,8 +1,20 @@
-pub mod axon;
-pub mod handler;
-pub mod sse;
-pub mod tools;
+//! `neuron-protocol` — re-export shim for the canonical Axon platform crates.
+//!
+//! All types now live in:
+//! - `axon-protocol` (`platform/protocols/axon/crates/axon-protocol`)
+//! - `axon-events`   (`platform/protocols/axon/crates/axon-events`)
+//!
+//! This crate re-exports everything so existing neuron-rs crates that import
+//! `neuron_protocol::*` continue to compile without changes.
 
-pub use axon::{AxonEvent, AxonMessage, AxonMethod, AxonResponse};
-pub use handler::AxonHandler;
-pub use tools::ProjectType;
+// Re-export wire-protocol types
+pub use axon_protocol::handler::AxonHandler;
+pub use axon_protocol::message::{AxonEvent, AxonMessage, AxonMethod, AxonResponse};
+pub use axon_protocol::sse::SseChannel;
+pub use axon_protocol::tools::{self, ProjectType, ALL_TOOLS};
+
+// Re-export event schema
+pub use axon_events::{
+    AxonEnvelope, AxonError, AxonRouter, AxonSubscription, EventId, ProjectContext, Severity,
+    Timestamp,
+};