The VFS bridge suspends the Monty worker for the length of a read. Monty checks
its duration budget between interpreter steps, so it cannot check while a read
is in flight. Code that reads in a loop overran a 60s budget by minutes. A read
takes about 20ms on a 2789-document corpus, so a full scan spends about 55s in
reads alone.
Check the deadline before each read. Raising from inside the callback answers the
worker's suspension, which keeps the session usable.
Monty also spends max_duration_secs across the session rather than per call, and
the sandbox reuses the session so that variables persist. Budget it for
code_timeout * max_executions. At the old per-call value the first slow call
starved every later one.
Do not wrap feed_run in asyncio.wait_for. Cancelling during pure compute is
clean, but cancelling while a read waits for an answer wedges the session with a
protocol RuntimeError that escapes execute(). A call that computes without
reading stays bounded by the session budget alone.
