feat: schema manifest, parity allow-list and lifecycle fixtures (#33)

The Voluptuous schema is now dumped into a deterministic committed
manifest (265 leaf paths); a pytest fails on drift. A parity test
compares manifest enums with the exported frontend const lists through
a machine-readable allow-list that also refuses to rot. The field
registry gains passports (allow-extra / lovelace-card), enforcedBy
citations for mechanisms that already shipped, and passports for the
v1.68-v1.69 fields; a completeness test bans dead decisions. Lifecycle
fixtures (oldest / current / future) prove lossless loading, and the
config auditor gains the 0/3/2 exit-code contract.

User-Visible: yes
Issue: #33

docs/ARCHITECTURE.md

@@ -1523,3 +1523,27 @@ other world honest against it:
   `enforcedBy`. The lifecycle fixtures in `test/fixtures/config-lifecycle/`
   pin the load contract: oldest-supported and future-field configs pass the
   schema losslessly.
+
+## Schema as the source of truth (#33, 2026-08-30)
+
+The Voluptuous schema in `custom_components/houseplan/validation.py` is the
+single owner of the persisted config/layout shape. Three artefacts keep every
+other world honest against it:
+
+- `scripts/dump-config-schema.py` walks the schema into the deterministic
+  `scripts/config-schema-manifest.json` (265 leaf paths at introduction);
+  a pytest regenerates it and fails on any uncommitted drift.
+- `test/config-schema-parity.test.mjs` compares manifest enums with the
+  exported frontend const lists (`DISPLAY_MODES`, `TAP_ACTIONS`,
+  `SPACE_FILL_MODES`/`ROOM_FILL_MODES`, `OPENING_TYPES`,
+  `VACUUM_TRAIL_MODES`, `ZERO_WALL_STYLES`, `BG_MODES`). Every divergence
+  must be blessed in `scripts/schema-compat-allowlist.mjs` with a reason and
+  an owning issue — and an allow-list entry that stops matching a real
+  divergence fails the test too, so the list cannot rot.
+- `scripts/config-field-registry.mjs` stays the DECISION layer on top of the
+  manifest: only fields with a non-trivial fate live there, each resolving to
+  a manifest path or carrying an explicit `schema: 'allow-extra'` /
+  `'lovelace-card'` passport; implemented mechanisms cite their code point in
+  `enforcedBy`. The lifecycle fixtures in `test/fixtures/config-lifecycle/`
+  pin the load contract: oldest-supported and future-field configs pass the
+  schema losslessly.

docs/CHANGELOG.md

@@ -2,6 +2,13 @@
 
 ## Unreleased
 
+- Old and future plan configs are now guarded by machinery instead of habit:
+  the backend schema is dumped into a committed manifest, frontend and
+  backend value lists are compared in CI with an explicit allow-list for the
+  few legitimate compatibility divergences, and lifecycle fixtures prove a
+  config from the oldest supported era — or one from the future — loads
+  without silent loss ([#33](https://github.com/Matysh/houseplan-card/issues/33)).
+
 - Old and future plan configs are now guarded by machinery instead of habit:
   the backend schema is dumped into a committed manifest, frontend and
   backend value lists are compared in CI with an explicit allow-list for the

docs/CHANGELOG.ru.md

@@ -8,6 +8,13 @@
 
 ## Не выпущено
 
+- Старые и будущие конфигурации плана теперь защищены механикой, а не
+  привычкой: схема бэкенда выгружается в закоммиченный манифест, списки
+  значений фронта и бэкенда сверяются в CI с явным allow-list'ом немногих
+  легитимных компат-расхождений, а lifecycle-фикстуры доказывают, что конфиг
+  старейшей поддерживаемой эпохи — или из будущего — загружается без тихих
+  потерь ([#33](https://github.com/Matysh/houseplan-card/issues/33)).
+
 - Старые и будущие конфигурации плана теперь защищены механикой, а не
   привычкой: схема бэкенда выгружается в закоммиченный манифест, списки
   значений фронта и бэкенда сверяются в CI с явным allow-list'ом немногих