fix(go): repair migration wire contracts and runtime lifecycle; document incomplete port

pkg/protocol/method_registry.go

@@ -27,6 +27,13 @@ var (
 	isRegistryLoaded   bool
 )
 
+func init() {
+	for name, id := range canonicalMethodIDs {
+		nameToIdMap[name] = id
+		idToNameMap[id] = name
+	}
+}
+
 // LoadMethodCatalog loads the method catalog from a JSON file (e.g. data/client_data/MethodIds.json).
 func LoadMethodCatalog(path string) error {
 	data, err := os.ReadFile(path)
@@ -72,10 +79,11 @@ func GetMethodID(name string) (uint32, bool) {
 	return id, ok
 }
 
-// MethodGetMethodIDDefault returns the numeric ID for a method name or a fallback.
+// MethodGetMethodIDDefault resolves a verified name. Legacy callers still pass
+// a fallback, but guessed IDs must never be sent to an unrelated client handler.
 func MethodGetMethodIDDefault(name string, fallback uint32) uint32 {
 	if id, ok := GetMethodID(name); ok {
 		return id
 	}
-	return fallback
+	return 0
 }