Add BNEP support

[colemancda]

Summary

Adds Personal Area Networking support via the kernel's BNEP module, turning the previously empty BNEP target into a working session-management layer:

• BNEPSocket — control socket for kernel network encapsulation sessions: addConnection bridges a connected L2CAP socket (PSM 15) into a virtual Ethernet interface and returns the created interface name (e.g. bnep0); removeConnection destroys a session; connections() lists active sessions; supportedFeatures() reads the kernel feature bitmask.
• Ioctl wrappers for all four operations, following the existing RFCOMM wrapper pattern (the ioctl identifiers already existed in BNEPIO but had no request types). The connection list request embeds a pointer to a caller-allocated array rather than a flexible array member, so the wrapper allocates and wires the buffer internally.
• C interop structures matching the kernel ABI, with fixed 16-byte interface name buffers and destination addresses in network (Ethernet) byte order.
• Value types — BNEPRole (PANU, NAP, GN service classes), BNEPConnectionFlag, BNEPConnectionState, and a public BNEPConnection info struct.

Establishing a PAN link end to end additionally requires a classic L2CAP connection to PSM 15 and the setup request/response exchange; classic L2CAP connect conveniences are a natural follow-up (current helpers are LE-only).

Test plan

• 7 new unit tests using the syscall mocking driver: ioctl request codes asserted against exact kernel values (including sign extension of read-direction requests), struct memory layouts asserted against the C ABI, faked kernel replies for add connection (interface name write-back), connection list, and supported features, and device name encoding round-trips
• Full test suite passes (57 tests)
• swift build succeeds with no new warnings
• Live behavior requires Linux with the kernel BNEP module and CAP_NET_ADMIN (root)