Foremerge v0.3.0

Known defect: use 0.3.1 instead

Every time this version opens a coordination store it writes a duplicate
"detection" row for any conflict that already recorded one, so a single
detection shows two observations while the event log records one. The
duplicate cannot be deleted afterwards, because the append-only trigger that
protects those rows blocks removal.

This version also has three further defects fixed in 0.3.1: a validation could
pass using an excluded generated file that is not in the accepted commit, an
interrupted upgrade could silently drop intents from scope queries, and the
documented 30 second shutdown was not an exit bound.

Upgrade to 0.3.1, which repairs affected stores automatically the first
time it opens them. No manual cleanup is needed, and observations that
genuinely differ are preserved.

Full Changelog: v0.2.0...v0.3.0