Cuts v0.14.0 covering #107 (PreIteration mid-loop hook) and #108 (Finish
completion-signal tool / :submitted termination), and registers
ExAthena.Tools.Finish in the hexdocs Builtin tools group.

Also backfills the v0.13.0 CHANGELOG entry: 0.13.0 was published to Hex
(the #103 dynamic-compaction-budget feature) from an unmerged branch, so
main's CHANGELOG never recorded it. v0.13.0 is now tagged at the
published commit (6fed70f).