Closes m2's last open box. The delivery_worker now wires its retry
loop on erlang:send_after / cancel_timer self-casts: failing flush
arms the per-Cid backoff timer; handle_info({retry, Cid}) redrives
one Cid through deliver_one_pure; success clears state, failure
schedules next slot or dead-letters on attempt 6.
m2 carries three cherry-picks of the send_after substrate work
(originally landed on loops/erlang via 3709460d/98b0104c/b10e55f0).
Those same commits are already on this architecture via the earlier
loops/erlang merge (154681a4); merging m2's duplicates is a
mechanical conflict-resolve to whichever copy git picks first.
Highlights since the previous m2 merge (2bafb4f7):
- 8b-timer wiring + 5 new tests in delivery_retry_timer.sh
- :timers state field tracks live refs; cancel_timer_for before
re-arming so stale timers don't keep the scheduler alive
- state_srv/1 + timer_ref_for/2 for test introspection
- merge-prep note documenting the duplicate-fix rebase strategy
m2 is now feature-complete. Conformance gate 771/771.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
# Conflicts:
# lib/erlang/conformance.sh
# lib/erlang/scoreboard.md
giles
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