libmicrovmi: VBoxVMI method at the VM's default socket #315

Parent

#312

What to build

An explicit VBoxVMI method selection no longer needs a socket path. When omitted, the Driver resolves the VM name to its UUID and reads its VBoxInternal/VMI/SocketPath extradata through the VirtualBox API, using <VirtualBox user home>/vmi/<VM UUID>.sock when unset. The socket path becomes optional in Rust, C (access_method VBoxVMI with null socket_path, previously an error) and Python. Only available when both access methods are compiled in; with VBoxVMI alone, a path is still required.

Acceptance criteria

• Explicit VBoxVMI without a path connects to the default socket of the named VM
• The SocketPath extradata override is honoured
• VBoxVMI-only builds reject a missing path with a clear error
• Rust, C and Python callers updated, including the integration harness and examples
• Integration test covers default path and extradata override