Problem: the hooks API conflated distinct lifecycle scopes under a flat
table with inconsistent naming (setup_code, before_run, setup_io_input),
making it hard to reason about when each hook fires.
Solution: introduce two namespaces — hooks.setup.{contest,code,io} for
one-time initialization and hooks.on.{enter,run,debug} for recurring
events. hooks.setup.contest fires once when a contest dir is newly
created; hooks.on.enter is registered as a buffer-scoped BufEnter
autocmd and fires immediately after setup.code. The provisional buffer
setup_code callsite is removed as it ran on an unresolved temp buffer.
Barrett Ruth
add022af8c