feat(soul): add sessions layer, MCP connectors, conversation continuity fix

- sessions.el: new sessions module with session management and approval gate
- routes.el: wire /api/sessions routes (list, get, create, approve, tool_result)
- chat.el: thread-aware activation — short messages anchor to last reply
  before engram compilation so follow-ups stay on-topic
- chat.el: agentic path tracks per-session history (session_hist_{id})
  instead of shared conv_history, seeding each turn with prior context
- chat.el: add call_neuron_mcp, dispatch_tool, is_builtin_tool, next_bridge_id
  agentic_loop, bridge_save, agentic_resume, handle_tool_result
- dist/soul: rebuild with all of the above

dist/semantics.c

@@ -291,3 +291,8 @@ el_val_t sem_realize_lang(el_val_t frame, el_val_t lang_code) {
   return 0;
 }
 
+int main(int _argc, char** _argv) {
+  el_runtime_init_args(_argc, _argv);
+  return 0;
+}
+