Add tests to ensure that cloudflare MCPAgent changes work with durable objects instrumentation

[AbhiPrasad]

Description

cloudflare/agents#415

npm i https://pkg.pr.new/cloudflare/agents@415

Cloudflare is making some changes to MCPAgent. We should make sure that our durable objects instrumentation still works as expected with this (as MCPAgent just wraps durable objects). https://github.com/getsentry/sentry-mcp/blob/fc9318eb2c680c1118fbccfadc5691cca39373e1/packages/mcp-cloudflare/src/server/lib/mcp-agent.ts#L122

[linear]

JS-927 Add tests to ensure that cloudflare MCPAgent changes work with durable objects instrumentation