feat(#1289): lightweight /fork via session.branch_whole (#1303)

app/src/main/java/com/m57/hermescontrol/data/ws/WsMethods.kt

@@ -15,6 +15,7 @@ object WsMethods {
     const val SESSION_DELETE = "session.delete"
     const val SESSION_TITLE = "session.title"
     const val SESSION_BRANCH = "session.branch"
+    const val SESSION_BRANCH_WHOLE = "session.branch_whole"
 
     /** Replay recorded events newer than client's last-seen seq for a session. */
     const val SESSION_EVENTS_SINCE = "session.events.since"