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/myapp.c

@@ -14,6 +14,10 @@
 #include "request.h"
 #include "utils.h"
 
+/* forward declaration — implemented in startup_validation.c */
+int validate_startup_config(const char *config_path,
+                            char *warn_buf, size_t warn_len);
+
 time_t        last_print_time = 0;
 unsigned long npkts           = 0;
 unsigned long npkts_old       = 0;
@@ -70,6 +74,15 @@ int myapp_run(myconf_t* myconf)
         /* Role stays CTRL_STANDBY — already set by ha_init(). */
     }
 
+    /* Req 4.4: warn if config file contains deprecated 'vcpus' key */
+    {
+        char warn_buf[256] = {0};
+        validate_startup_config(myconf->conffile, warn_buf, sizeof(warn_buf));
+        if (warn_buf[0]) {
+            WARN("startup: %s", warn_buf);
+        }
+    }
+
     /* Phase 2: full init (requires cluster_config) */
     rc = cluster_init_phase2(&c);
     if (rc < 0) {