feat(engram): ML-KEM-1024 PQC encryption, nomic embeddings, MCP routes, checkpoint-per-write

- Add ML-KEM-1024 + AES-256-GCM binary persistence to el_runtime.c with
  two-key scheme (Neuron master + user key); SHAKE-256 key derivation
- Add nomic-embed-text 768-dim float32 embeddings on every node write
  via Ollama; graceful fallback when Ollama is not running
- Wire all /api/neuron/* MCP routes directly into Engram (server.el),
  eliminating the Kotlin server as the MCP backend
- Set ENGRAM_CHECKPOINT_INTERVAL = 1 (write binary on every node write,
  not every 50)
- Add el_runtime.h declarations for engram_write_binary_el and
  engram_load_binary_el builtins

lang/elb.el

@@ -312,7 +312,7 @@ fn link_binary(c_files: [String], out_bin: String, runtime_path: String, out_dir
     let master_decls: String = out_dir + "/elp-c-decls.h"
     let has_master: String = str_trim(exec_capture("test -f " + master_decls + " && echo yes || echo no"))
     let include_flag: String = if str_eq(has_master, "yes") { "-include " + master_decls } else { "" }
-    let parts = native_list_append(parts, "cc -O2 " + bracket_flag + " " + ossl_inc_flag + " " + include_flag + " -I " + dirname_of(runtime_path) + " -I " + out_dir)
+    let parts = native_list_append(parts, "cc -O2 -DHAVE_CURL " + bracket_flag + " " + ossl_inc_flag + " " + include_flag + " -I " + dirname_of(runtime_path) + " -I " + out_dir)
     let i = 0
     while i < n {
         let f: String = native_list_get(c_files, i)