refactor(gui): features register their own settings surfaces

Settings collaboration direction (recorded in the note): the shell only
provides composition faces — feature plugins register themselves. The
General section moves into the ui-settings shell (order 0, skeleton
rows) and declares the settings.general.item list slot; locale registers
the Language row and ui-theme the Appearance row (each with its own
store mirror, dictionaries, and ledger-judged deferral); the
ui-settings-general package is gone. ui-settings-models becomes
ui-models — a feature package that contributes its Settings section
rather than a settings-owned satellite. The item-slot SlotMap entry is
authored in the ui-settings contract and repeated verbatim in
locale/ui-theme (reference-cycle avoidance; declaration merging keeps
the copies identical).

apps/cli/cordis.yml

@@ -233,11 +233,8 @@
 - id: ui-settings
   name: '@deepseek-ai/dsh-client-ui-settings'
 
-- id: ui-settings-general
-  name: '@deepseek-ai/dsh-client-ui-settings-general'
-
-- id: ui-settings-models
-  name: '@deepseek-ai/dsh-client-ui-settings-models'
+- id: ui-models
+  name: '@deepseek-ai/dsh-client-ui-models'
 
 - id: ui-conversation
   name: '@deepseek-ai/dsh-client-ui-conversation'