refactor(client): replace the per-field settings preference controller with a namespace settings scope

bindSettingsScope mirrors the Host-side settings owner seam in the browser:
one scope per namespace publishes a snapshot store (status, section value,
revision, writability, host/memory mode), validates sections against the
namespace's serialized wire schema via dsh-client-schema-form, and keeps the
controller's listener-before-read, revisioned serialized writes, latest-wins
publication, conflict recovery, and disposal quiescence. Theme, locale, and
busy-Enter services now take the scope as a constructor collaborator, which
removes the bindPersistence/syncPreference two-phase callback pair and the
defaulted no-op persist writers; hand-written wire guards fall away in favor
of the registered schema. test-runtime gains a stubSettingsScope double.

packages/client/ui-theme/src/invariant.ts

@@ -15,10 +15,10 @@ export const name = 'client-ui-theme-invariant'
 export const inject = ['invariants']
 
 /**
- * No runtime invariant: the settings seam validates and publishes the durable
+ * No runtime invariant: the settings scope validates and publishes the durable
  * theme section, while the registry emits `theme/change` synchronously with
  * its own mutations. Store/registry agreement is covered directly by this
- * package's Host, controller, and service behavior specs.
+ * package's Host, scope, and service behavior specs.
  */
 const install: InvariantInstaller = () => {}