Mock cheap-model adapter endpoints in Storybook fixtures

The AgentConfigForm cheap-model section reads /api/adapters and
/api/companies/:id/adapters/:type/{models,model-profiles}. Mocking these
in the Storybook preview lets stories render the new section against
realistic adapter capability data instead of falling back to the
client-side defaults.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

ui/storybook/.storybook/preview.tsx

@@ -87,6 +87,63 @@ function installStorybookApiFixtures() {
       });
     }
 
+    if (url.pathname === "/api/adapters") {
+      return Response.json([
+        {
+          type: "claude_local",
+          label: "Claude Local",
+          source: "builtin",
+          modelsCount: 2,
+          loaded: true,
+          disabled: false,
+          capabilities: {
+            supportsInstructionsBundle: true,
+            supportsSkills: true,
+            supportsLocalAgentJwt: true,
+            requiresMaterializedRuntimeSkills: false,
+            supportsModelProfiles: true,
+          },
+        },
+        {
+          type: "codex_local",
+          label: "Codex Local",
+          source: "builtin",
+          modelsCount: 3,
+          loaded: true,
+          disabled: false,
+          capabilities: {
+            supportsInstructionsBundle: true,
+            supportsSkills: true,
+            supportsLocalAgentJwt: true,
+            requiresMaterializedRuntimeSkills: false,
+            supportsModelProfiles: true,
+          },
+        },
+      ]);
+    }
+
+    const adapterModelsMatch = url.pathname.match(
+      /^\/api\/companies\/[^/]+\/adapters\/([^/]+)\/(models|model-profiles)$/,
+    );
+    if (adapterModelsMatch) {
+      const [, , resource] = adapterModelsMatch;
+      if (resource === "models") {
+        return Response.json([
+          { id: "claude-opus-4-7", label: "Claude Opus 4.7" },
+          { id: "claude-sonnet-4-6", label: "Claude Sonnet 4.6" },
+          { id: "claude-haiku-4-5", label: "Claude Haiku 4.5" },
+        ]);
+      }
+      return Response.json([
+        {
+          key: "cheap",
+          label: "Cheap",
+          adapterConfig: { model: "claude-sonnet-4-6" },
+          source: "adapter_default",
+        },
+      ]);
+    }
+
     if (url.pathname === "/api/plugins/ui-contributions") {
       return Response.json([]);
     }