FIX 1 — UDP 9100 binding race: SprtDiscoveryServiceTests and
CompositeDiscoveryServiceTests both use exclusive UDP 9100 binds. xunit
runs test classes concurrently by default, causing the tests to fail
intermittently with AddressAlreadyInUse. Add [Collection("udp-9100")]
attribute to both classes so they run serially instead.
FIX 2 — Design doc: CompositeDiscoveryService does NOT forward the callback
down to children; it raises the caller's callback itself after all children
finish, once per unique IP. Rewrite the relevant sentence to describe the
real behavior.
Verify: 30 tests pass (x2), build clean, no production code touched.
Claude-Session: https://claude.ai/code/session_01E6N3P4nSZLtp4BC2LXVref
b42d980877