R07 U7: Driver.Cli.Common gains RunCancellableAsync (moved up from AbLegacy) and
CreateChangeLineWriter (one lock-serialised line per change; a failing console
write is logged and swallowed so it cannot fault the poll loop). AbCip
probe/read/write print Cancelled. on Ctrl-C instead of a stack trace, and AbCip
subscribe uses the shared writer. SnapshotFormatter renders arrays/lists as
[a, b, c] instead of System.Int32[].
Refs #747
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
Joseph Doherty
f9fbd4ee0d