bug(sdk): native Headers entries are lost when configuring client scope

Description

The JavaScript SDK drops entries from a native Headers instance when createOpencodeClient also receives a nonempty directory (v1/v2) or experimental_workspaceID (v2). The wrapper spreads config.headers into an object, which does not copy native header entries. This can turn valid requests to a password-protected OpenCode server into HTTP 401 responses.

Plain object headers and clients without either scope setting do not reproduce this issue.

Steps to reproduce

Run with Bun from a project using @opencode-ai/sdk:

import { createOpencodeClient } from "@opencode-ai/sdk/v2/client"

const server = Bun.serve({
  hostname: "127.0.0.1",
  port: 0,
  fetch: () => Response.json([]),
})
const client = createOpencodeClient({
  baseUrl: server.url.href,
  directory: "/tmp/project",
  headers: new Headers({ authorization: "Bearer example" }),
})
const result = await client.project.list()
console.log(result.request.headers.get("authorization"))
server.stop(true)

Expected: Bearer example. Actual: null. Replacing new Headers(...) with a plain object preserves the header. The same issue occurs with v1, and with v2 workspace-only configuration.

OpenCode version

Source checkout 5cf9f517cfec3ef68d3e68a12a6a4b3163947f44 (@opencode-ai/sdk 1.18.28); the affected wrappers remain unchanged at upstream 02a167e048d3bd7299225068d79e4fce5c830d67.

Operating System

macOS arm64, Bun 1.3.14.