message: add some todo/working-on items
diff: generate ACK // EKR
  consume ACK // EKR
  +Track ooo ACK ranges in SendStream // grover
  +Track dropped ranges in SendStream and queue for resend // grover
  +Add stream events to transport API (readable, writable, new, closed) // grover
  +Use stream events in h3 // grover or dragana?
  client/server cmdline
  harmonize our rust usage:
  - use foo::* or use foo::{bar, baz} and ordering/grouping
  