restructure: move el compiler content into lang/

lang/examples/activate.el

@@ -0,0 +1,54 @@
+// activate.el — The `activate` construct: spreading activation over the type graph.
+//
+// The `activate` keyword is the most novel feature of the Engram language.
+// Instead of querying a database with SQL or a key lookup, you query the
+// *type graph* using a natural language description. The result is
+// statically typed — the compiler knows you get [User] back, not Any.
+//
+// How it works:
+//
+// 1. At compile time, the type checker verifies that `User` is a registered
+//    type with a corresponding Engram node mapping.
+//
+// 2. At runtime, the Engram runtime performs spreading activation over
+//    the knowledge graph, starting from the User node, propagating to
+//    semantically related nodes with co-activation energy proportional
+//    to edge weights and node salience.
+//
+// 3. The query string "customer who purchased recently" is embedded
+//    and used as a semantic filter: only nodes whose embeddings are
+//    within cosine-similarity threshold of the query embedding are returned.
+//
+// 4. The result is type-safe: [User]. You don't get back Any or a JSON blob.
+//    The type checker enforces this at compile time.
+
+type User {
+    id: Uuid
+    name: String
+    email: String
+}
+
+type Order {
+    id: Uuid
+    user_id: Uuid
+    amount: Float
+    status: String
+}
+
+// Query: find all users who are semantically related to "customer who purchased recently"
+// The result type is [User] — an array of User nodes from the knowledge graph.
+let recent_buyers: [User] = activate User where "customer who purchased recently"
+
+// You can also activate on other types:
+let pending_orders: [Order] = activate Order where "order awaiting fulfillment"
+
+// Spreading activation respects the type graph edges.
+// If User and Customer share an Engram node type (e.g. "Entity"),
+// they are semantically compatible — the type checker allows
+// treating one as the other when they map to the same Engram node class.
+
+fn process_buyers(users: [User]) -> String {
+    return "processing users"
+}
+
+let result: String = process_buyers(recent_buyers)