feat(mcp): upgrade client SDK to v2 (#39247)

Co-authored-by: Matt Carey <mcarey@cloudflare.com>

packages/opencode/test/mcp/oauth-callback.test.ts

@@ -74,7 +74,7 @@ describe("McpOAuthCallback.ensureRunning", () => {
     const response = await fetch(`${redirectUri}?code=code&state=success`)
 
     expect(response.status).toBe(200)
-    expect(await callback).toBe("code")
+    expect(await callback).toEqual({ code: "code", iss: undefined })
     expect(McpOAuthCallback.isRunning()).toBe(false)
   })