- Transport: expose LastRecvOldNum/LastRecvNewNum for state tracking
- WASM: stateTracker with shadow VT emulator and received states map
- Each diff applied to base state copy, stored by newNum
- Display diffing: only changed cells sent to terminal
- Eliminates garbled output from missed diffs and state transitions
- Build with -tags osusergo for WASM os/user compatibility
The Dart mosh client only calls sendNew() when hasPendingState is false.
The Go client was calling SetPending on every tick with dirty=true, which
reset diffSent and caused new sequence numbers for the same cumulative
payload. Now tick() checks AckedByRemote >= SentNum before calling
SetPending — at most one unacked state in flight, matching the Dart
client's behavior.