refactor(llm-deepseek)!: rename the provider route to deepseek-official

The native adapter's route was named deepseek, colliding with pi-ai's
catalog provider of the same name, so the two DeepSeek paths could never
be mounted side by side. The web settings page needs both configurable at
once. Compositions, fixtures, goldens, scaffolding defaults, and docs all
move together (pre-release, no shim); TUI/session-query-spill/
missing-credential goldens re-recorded through their keyless refresh
modes because provider-name length shifts box padding and spill
truncation points.

packages/sdk/helper/src/features/builtin/index.ts

@@ -154,7 +154,7 @@ config:
       ],
       options: [
         {
-          id: 'deepseek',
+          id: 'deepseek-official',
           label: 'DeepSeek search',
           default: true,
           markers: [{ id: 'web-search-deepseek', name: '@deepseek-ai/dsh-web-search-deepseek' }],

packages/sdk/helper/src/features/builtin/provider.ts

@@ -20,7 +20,7 @@ const DEFAULT_MODEL = 'deepseek-v4-flash'
 const API_KEY_COMMENT = 'Required before start; an empty value makes provider startup fail.'
 
 class DeepSeekOption extends FeatureOption {
-  override readonly id = 'deepseek'
+  override readonly id = 'deepseek-official'
   override readonly label = 'DeepSeek'
   override readonly secrets = [{
     id: 'apiKey',
@@ -76,7 +76,7 @@ export class ProviderFeature extends ExclusiveOptionFeature {
 
   /** Prefer the direct-fetch adapter and its public endpoint defaults. */
   override defaultOptions(): readonly string[] {
-    return ['deepseek']
+    return ['deepseek-official']
   }
 
   /** Recover literal endpoint overrides from either provider entry. */