Basic implementation of /commit, /version, and /status

No precondition checking, persistence, or log scanning yet.

src/connection.hpp

@@ -209,7 +209,7 @@ struct Connection {
    * metrics.recordQueueDepth(conn->get_id(), conn->outgoingBytesQueued());
    * ```
    */
-  int64_t outgoingBytesQueued() const {
+  int64_t outgoing_bytes_queued() const {
 #ifndef NDEBUG
     // Debug build: validate counter accuracy
     int64_t computed_total = 0;