open_tick, close_tick and close_ticks_before lose `pub`: run_tick through
open_or_find is the only caller, and a compile_fail doctest pins that an
exported-type holder cannot call them. open_tick uses
OwnedRedbMessagePackBackingStore::insert_entry_if_absent in one write
transaction instead of read-then-push, so two opens of one ordinal cannot both
succeed. Fixes s2 tick-rows-have-a-public-writer and open-tick-is-check-then-put.
Builds.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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