feat(ha-config-bootstrap): implement --vcpus CLI, wire validation, remove vcpus from config (task 2.2)

- Add --vcpus N argp option in main.c; store in myconf.vcpus
- Replace inline argp guard with validate_vcpus() call (returns -EINVAL for <=0)
- Add validate_startup_config() in startup_validation.c: returns 0; writes
  deprecation warning into caller-supplied warn_buf when vcpus key present
- Wire validate_startup_config() into myapp_run() after conffile resolved;
  emit WARN() if warn_buf non-empty (Req 4.4)
- Remove vcpus field from cluster_config_t (clusterconfig.h)
- Preserve capnp ordinal: vcpus @7 -> vcpusDeprecated @7: Void in controller.capnp
- vtaskmgr_init uses only myconf->vcpus with hardcoded default 8
- Add stub C types in typemap.h for capnp schema extensions from task 1.1
- 96 tests pass

src/controller/config_repl.c

@@ -46,7 +46,6 @@ static void fill_default_cluster_config(cluster_config_t *c)
 {
     SET_DEFAULT_IF_UNSET(c->port, 0, 9990);
     SET_DEFAULT_IF_UNSET(c->heartbeat_interval, 0, 5);
-    SET_DEFAULT_IF_UNSET(c->vcpus, 0, 8);
     SET_DEFAULT_IF_UNSET(c->fetch_job_interval, 0, 10);
 }