fix(scan): probe every NIC's subnet broadcast for VXI-11 discovery

[ShortArrow]

Problem

visa scan returned 0 results on multi-homed hosts even when an instrument was on a directly-connected subnet. The scanner bound to IPAddress.Any and sent only to the limited broadcast 255.255.255.255, which egresses a single interface on Windows (the default route's). An instrument on a secondary lab NIC never received the probe.

Confirmed against a real Kikusui PWR801L (192.168.3.100) reached via a host's secondary 192.168.3.10 NIC — its 255.255.255.255 probes were going out an unrelated APIPA interface.

Change

Vxi11BroadcastScanner.ScanAsync now:

• Enumerates every operational, non-loopback IPv4 interface.
• For each, computes the subnet-directed broadcast (ip | ~mask, e.g. 192.168.3.255), binds a UdpClient to that NIC's local address, and sends the GETPORT there.
• Probes all interfaces concurrently and de-duplicates responders by sender IP.
• Skips interfaces that fail to bind/send (APIPA, tunnels) without aborting the scan.

Also unmasks the discovered resource in visa scan output: it now prints the real host (FormatResource) in human + --json output instead of the ToLogString-masked ***. ToLogString masking is scoped to logging (ADR 0017), not user-requested discovery output, and matches what --add already writes to config.

mDNS multi-interface tuning is left as-is (Makaretu binds all interfaces by default); the VXI-11 broadcast path is the verified fix.

Verification

• Unit tests (TDD): DirectedBroadcast (per-subnet host-bit computation, 4 cases) and ShouldProbe (interface filter: up/loopback/IPv4/mask). Socket round-trip verified on hardware per ADR 0008 §Verification.
• Real device: on the secondary-NIC host, ivicli visa scan --json went from (no resources discovered) to:
  {"discovered":[{"index":1,"resource":"TCPIP0::192.168.3.100::inst0::INSTR","idn":null}]}

Full suite green (Category!=Integration), csharpier + analyzers clean.

Docs

ADR 0008 §3 updated in-place: per-NIC directed broadcast, shared Vxi11Portmapper codec, and the inherent cross-subnet / broadcast-only limits. §4 notes the unmasked scan output.