## os.rkt and friends

 - move from quasiquoted to prefab structs
 - define a prefab struct for every evt? that we want to use
 - define lowest-level drivers for each prefab struct

It feels like those lowest-level drivers are listening for *demand*
i.e. they're listening for presence and are then acting to supply such
demand. Think about the relationships between presence (both positive
and negative), and interfacing to ad-hoc sources and sinks.

### Old, possibly-still-relevant TODOs from os.rkt

 - is timeout really primitive? If so, isn't presence primitive?
 - what about metatimeout?
 - enforce user-mode restrictions

### Abstract out UDP socket creation

### Things to consider doing to os-big-bang.rkt

 - add contracts on structs used as message types e.g. to catch such
   as #(192 203 230 10) being used instead of (udp-address
   "192.203.230.10" 53).

 - some kind of join-ish construct to make e.g. cname-expansion
   prettier

 - have a "terminate" kind of transition for unspawning the
   transitioning process