The WebSocket control-frame heuristic only recognized resize/ack/reset,
so the frontend's heartbeat reply {"type":"pong"} fell through to
write_input() and was typed into the shell / pi every ~30s. That garbage
corrupted the foreground app: stray text in the input line, rerenders,
and scroll-position resets (visible on resize/scroll redraws).
Treat any text frame that parses to a JSON object carrying a "type" field
as control traffic that must NEVER reach the PTY: handle known types and
ignore unknown ones. Keystrokes, bracketed-paste content, and plain text
are still forwarded as raw input.
Developer
ff7fcb6e8d