fix: preserve full OpenCode provider cost shape in auth.loader

The normalizeProviderModelCosts function was only setting { input: 0, output: 0 }
which doesn't match the full OpenCode provider cost shape that includes cache fields.

This fix:
- Preserves existing cost fields (input, output, cache.read, cache.write) if valid
- Adds missing cache: { read: 0, write: 0 } structure when not present
- Validates provider and model objects before modification to avoid poisoning
  invalid provider metadata
- Updates ProviderModel type to include optional cache field

Fixes provider cost normalization to maintain cache field compatibility.

packages/plugin/src/tui.ts

@@ -70,6 +70,23 @@ export type TuiRouteDefinition = {
   render: (input: { params?: Record<string, unknown> }) => JSX.Element
 }
 
+/** @deprecated Use api.keymap.registerLayer({ commands, bindings }) instead. */
+export type TuiCommand = {
+  title: string
+  value: string
+  description?: string
+  category?: string
+  keybind?: string
+  suggested?: boolean
+  hidden?: boolean
+  enabled?: boolean
+  slash?: {
+    name: string
+    aliases?: string[]
+  }
+  onSelect?: () => void
+}
+
 export type TuiKeys = {
   formatSequence: (parts: readonly KeySequenceFormatPart[] | undefined) => string
   formatBindings: (bindings: readonly SequenceBindingLike[] | undefined) => string | undefined
@@ -463,6 +480,12 @@ export type TuiPluginApi = {
   app: TuiApp
   keys: TuiKeys
   keymap: TuiKeymap
+  /** @deprecated Use api.keymap.registerLayer({ commands, bindings }) instead. */
+  command: {
+    register: (cb: () => TuiCommand[]) => () => void
+    trigger: (value: string) => void
+    show: () => void
+  }
   route: {
     register: (routes: TuiRouteDefinition[]) => () => void
     navigate: (name: string, params?: Record<string, unknown>) => void