Release 0.2.2

Bump the manifest to 0.2.2 and add CHANGELOG.md with upgrade, reset and
rollback notes covering all reliability work since 0.2.1. The README
drops its accumulated "Unreleased" sections in favor of the changelog
and gains a Diagnostics section explaining the Status attributes and how
to choose freshness limits. The package check now fails if the manifest
version has no changelog entry. ROADMAP marks the Milestone 0 items now
backed by tests and resets the next-session backlog; AUDIT.md records
this round's findings.

Still observation-only. Tested in the HA Core harness with HA 2025.12.0
and 2026.2.3; not on HAOS.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

custom_components/heating_mpc/manifest.json

@@ -9,5 +9,5 @@
   "iot_class": "local_polling",
   "requirements": [],
   "single_config_entry": true,
-  "version": "0.2.1"
+  "version": "0.2.2"
 }