Migrate UI to v2 SDK client

Use v2 OpencodeClient with normalized request handling and rehydrate pending permissions via GET /permission on instance hydration.

packages/ui/src/lib/opencode-api.ts

@@ -0,0 +1,37 @@
+import type { OpencodeClient } from "@opencode-ai/sdk/v2/client"
+
+export class OpencodeApiError extends Error {
+  constructor(message: string, options?: { cause?: unknown }) {
+    super(message)
+    this.name = "OpencodeApiError"
+    if (options && "cause" in options) {
+      ;(this as any).cause = options.cause
+    }
+  }
+}
+
+type RequestResultLike<T> =
+  | {
+      data: T
+      error?: undefined
+    }
+  | {
+      data?: undefined
+      error: unknown
+    }
+
+export async function requestData<T>(
+  promise: Promise<RequestResultLike<T> | undefined>,
+  label: string,
+): Promise<T> {
+  const result = await promise
+  if (!result) {
+    throw new OpencodeApiError(`${label} returned no result`)
+  }
+  if ((result as any).error) {
+    throw new OpencodeApiError(`${label} failed`, { cause: (result as any).error })
+  }
+  return (result as any).data as T
+}
+
+export type { OpencodeClient }