fix: add missing Flag import in shared/ui.ts and align test with Bearer scheme

The embedded-UI loader referenced Flag.* without importing it, which would
throw ReferenceError at module evaluation and prevent the sidecar from
starting. Also updates the www-authenticate assertion in httpapi-ui.test.ts
to match the new Bearer scheme set in the authorization middleware.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: 2 people

packages/opencode/src/server/shared/ui.ts

@@ -1,4 +1,5 @@
 import { AppFileSystem } from "@opencode-ai/core/filesystem"
+import { Flag } from "@opencode-ai/core/flag/flag"
 import { Effect, Stream } from "effect"
 import { HttpBody, HttpClient, HttpClientRequest, HttpServerRequest, HttpServerResponse } from "effect/unstable/http"
 import { createHash } from "node:crypto"

packages/opencode/test/server/httpapi-ui.test.ts

@@ -387,7 +387,7 @@ describe("HttpApi UI fallback", () => {
       const response = yield* uiApp({ password: "secret", username: "opencode" }).request("/session")
 
       expect(response.status).toBe(401)
-      expect(response.headers.get("www-authenticate")).toBe('Basic realm="Secure Area"')
+      expect(response.headers.get("www-authenticate")).toBe('Bearer realm="Secure Area"')
     }),
   )