Add server-side builtins, import system, and http_serve for Neuron Code rewrite

- Import resolution: resolve_imports() pre-processes import statements by
  reading and concatenating referenced .el files before compilation
- http_serve builtin: tiny_http-based server on configurable port; POST
  /axon/message stores request in __request__ state, invokes handle_request
  entry point via sub-interpreter, reads __response__ state for reply
- New builtins: blake3_hash, uuid_new, fs_list_recursive, fs_mkdir, fs_exists,
  path_join, path_parent, str_trim, str_contains, str_replace, str_starts_with,
  str_ends_with, str_last_index_of, json_get, json_array_push, json_array_len,
  now_millis, http_get, http_post, int_to_str
- Catch-all arms in el-types and el-compiler for new AST variants (Import,
  ProtocolDef, ImplDef, Closure, Try, MapLiteral, TypeExpr::Result, TypeExpr::Map)
- Parser: decorators field on FnDef, import/protocol/impl parsing

crates/el-test/src/eval.rs

@@ -122,6 +122,8 @@ impl<'g> Evaluator<'g> {
             // Seed statements are handled before eval in the runner
             Stmt::Seed(..) | Stmt::TestDef { .. } | Stmt::Assert(..) => {}
             Stmt::FnDef { .. } | Stmt::TypeDef { .. } | Stmt::EnumDef { .. } => {}
+            // New statement kinds — skip
+            _ => {}
         }
         Ok(())
     }
@@ -298,6 +300,11 @@ impl<'g> Evaluator<'g> {
                 Ok(EvalValue::Nil)
             }
 
+            // New expression kinds — return Nil
+            _ => {
+                return Ok(EvalValue::Nil);
+            }
+
             Expr::Sealed(stmts) => {
                 for s in stmts {
                     self.exec_stmt(s)?;