docs(changelog): release v0.22.0

Rolls [Unreleased] into [0.22.0] and gives it the headline every release
section carries. Two things were done to the section first, both of which
the release skill asks for and neither of which the backfill had:

GROUPING. The section was 82 flat top-level entries with no sub-bullets,
for a release SMALLER than v0.21.0 (220 commits against 303) — which had
54 top-level and 35 sub-bullets. "Group, don't list" is the house rule and
the flat shape broke it. Seven waves are now one parent bullet each, with
the original entries nested beneath: workflows that load and then misbehave,
describe -> exec round trips that delete what they described, the SOAP
reference trio, the brain's four silent losses, widget spellings that check
accepted and storage dropped, the check/exec contract gaps, and the security
reconcile paths. Every entry's text is carried through unchanged — verified
that all 204 non-blank lines of the pre-grouping section are still present.
The result is 53 top-level and 38 sub-bullets, which is v0.21.0's shape.

MODE 2. a725383 arrived in the last sync with no changelog entry at all.
It is the third part of the #923 workstream, so merge/join, Mode 2 and
NORMALIZED are now one parent with three sub-bullets rather than two
unrelated-looking entries and a gap.

make build, make test and make lint all pass.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BNDe35kDNsMX5cz4Ahn4rk

Author: ako