memoryd: sync begins when Honcho is turned on, and conclusions are matched by peer

Co-Authored-By: ornith-1.5-35b-a3b <agent@wntrmute.dev>

crates/memoryd/tests/honcho_sync.rs

@@ -48,6 +48,7 @@ fn to_trusted() -> Action {
 /// 1 skipped.
 fn mixed(dir: &TempDir) -> Ledger {
     let mut l = Ledger::open(&dir.path().join("honcho.jsonl")).unwrap();
+    l.append(Record::Began { time: at(0) }).unwrap();
     let decided = |item: Item, action: Action| Record::Decided {
         time: at(0),
         item,