adaptSandboxInstance

Adapt a sandbox instance (v1 or v2) to SandboxInstanceV2.

This builds on adaptSandboxProtocol from deepagents, which handles the core protocol adaptation (BackendProtocol → BackendProtocolV2 and sandbox properties execute/id).

This function additionally preserves test-specific properties:

• isRunning (required)
• close (optional)
• initialize (optional)
• uploadFiles (required, though optional in base protocol)
• downloadFiles (required, though optional in base protocol)