fix: the adoption bodies are no longer declared Lit properties (#520)

#500 gave `_serverCfg` and `_layout` prototype accessors but left them in
`static properties`. Lit marks such a property `wrapped` and, on the FIRST
update, force-writes it into `changedProperties` with an `undefined` old
value even though nobody assigned anything (`reactive-element.js:249-252`
and `:880-886`). `willUpdate` reads that as a config replacement, raises
`_cfgEpoch`, the memoized model key changes, and a 60-room house builds and
paints its model a second time: measured 19 update cycles, 4 builds and 4
epochs against 18 / 3 / 3 before #500, worth ~550 ms of `modelReadyMs` and
the same on `firstStableRenderMs` (3355 against a 3000 ceiling).

The declaration goes; the bodies stay reactive through the owner —
`_adoption` → `onBodyReplaced` → `requestUpdate(field, previous)` — which
needs no declaration: `getPropertyOptions` falls back to the default and
`changed.has('_serverCfg')` works as before. `noAccessor: true` would not
help, `wrapped` is set before that flag is read. The trap is written above
`static properties`, where someone would put the declaration back.

`cache.entries.cleanFloor` returns to 100 in both interaction budgets: the
120 entries were the extra epoch re-keying the per-room cache, not a
property of the design — the reasoning in 914e8402 was wrong.

Witness: test/config-adoption-ownership.test.mjs pins that neither body is
declared; the mutant `adoption-bodies-declared-reactive` puts the
declaration back and reddens it.

The boot diagnostics of the previous three commits touch four private
members, so they are declared in the performance contract: `_buildModel` and
`_cfgEpoch` outright (both exist in every supported comparison base), and the
adoption entry point as a current/legacy pair — #500 turned the private
`_adoptStructuralResponses` into the public `_adoptAuthoritative`, and an
undeclared rename would have the counter report zero adoptions instead of
failing.

The same commits carried a `node_modules` symlink: `.gitignore` had the
pattern with a trailing slash, which does not cover a symbolic link, and
`git add -A` in a sandbox worktree committed it. The link is removed and the
pattern loses the slash; a mutant run on this branch failed with `EEXIST` on
it.

Issue: #520
User-Visible: no

src/houseplan-card.ts

@@ -2537,6 +2537,23 @@ export class HouseplanCard extends LitElement {
   private _holdTimer?: number;
   private _holdFired = false;
 
+  /**
+   * #520: `_serverCfg` и `_layout` здесь НЕ объявляются, хотя они реактивны.
+   *
+   * С #500 их тела принадлежат `_adoption`, а карточка видит их через
+   * собственные аксессоры прототипа. Lit на такое объявление ставит флаг
+   * `wrapped` (`createProperty`) и на ПЕРВОМ обновлении принудительно кладёт
+   * свойство в `changedProperties` со старым значением `undefined` — даже
+   * если никто ничего не присваивал. `willUpdate` читает это как замену
+   * конфига, поднимает `_cfgEpoch`, ключ памятки модели меняется, и большой
+   * дом собирает и рисует модель второй раз: +550 мс до первого устойчивого
+   * кадра (замерено против базы `a44fbd37`, 3 эпохи против 4).
+   *
+   * Реактивность даёт `_adoption` через `onBodyReplaced` → `requestUpdate`:
+   * `requestUpdate` не требует объявления, `getPropertyOptions` возвращает
+   * умолчание, и `changed.has('_serverCfg')` работает как прежде.
+   * `noAccessor: true` не помогает — `wrapped` ставится до его проверки.
+   */
   static properties = {
     _tabDrag: { state: true },
     _hdrH: { state: true },
@@ -2553,11 +2570,9 @@ export class HouseplanCard extends LitElement {
     narrow: { attribute: false },
     _config: { state: true },
     _space: { state: true },
-    _layout: { state: true },
     _devices: { state: true },
     _selId: { state: true },
     _toast: { state: true },
-    _serverCfg: { state: true },
     _mode: { state: true },
     _tool: { state: true },
     _wallDialog: { state: true },