CUBELinux-2
c36f64c78d
Two correctness bugs found via ad-hoc daemon verification (T5 was
compile-verified only before):
1. decode_wal dropped WalOp::Txn entries on replay: the txn encoder emits
{"seq","op":"txn","batch"} with NO c/z/y/x fields, but decode_wal
read c/z/y/x unconditionally -> field_u8("c") returned Err -> the
whole entry was skipped. Committed transactions silently vanished on
restart. Fix: branch on op=='txn' before the c/z/y/x extraction.
2. commit was not synchronously durable: append_txn only buffered to the
WAL pending buffer; fsync happened on the 25ms group thread. A
clean stop within that window lost the commit. Fix: commit_txn now
calls wal.flush_pending() (fsync) before returning, so COMMIT is
durable on return -- a real transaction boundary.
Adds unit test commit_replays_from_wal_without_checkpoint (would have
failed before fix 1). Ad-hoc verifier exercises all 3 changed paths on
the live cube-server socket.