This PR adds a mechanism for notifying the client when a channel note
has been edited or a message has been changed.

TODO: 
- [x] Fix infinite loop when opening the chat panel
- [x] Switch to client-side ack model of observation detection
- [x] Add client-side-only change detection (e.g. for when a channel
note is open locally but not focused)
- [x] Review implementation / query performance.
- [x] Fix lack of ACK on restart for channel buffers
- [x] remove channel note opening on click
- [x] Fix channel messages sent while chat channel is in the background
not showing the channel as changed.

Release Notes:

- N/A