SceneSettingsStore

The scene level, over `Construct::sceneSettings` (§SS-6.4).

In the namespace construct::settings. Declared in src/libs/libconstruct/construct/settings/SceneSettingsStore.hpp.

Detailed description

No new store: `rendering.*` already carries the whole look/quality set and serializes with the document for free, exactly as `animation.*` does. This adapter only translates canonical ids into that key shape, via config::Schema::storageKey().

It also honours one read-only compatibility ramp: a setting with a `legacySceneKey` falls back to it when its own key is absent, so a scene saved before the key was renamed still resolves. The legacy key is never written — see SettingDef::legacySceneKey and §AQ-3.2.

⚠ Every write reaches `Construct::setSceneSetting`, which emits `sceneSettingsChanged()` *and* `emitSceneChanged()`; the latter re-snapshots the entire scene under the worker viewport. Writes driven by a drag must therefore be rate-limited by the caller (§SS-12) — this store deliberately does no limiting of its own, because it cannot tell a drag from a committed edit.