instrument_index only resolved {"node"} ends of a signal line, so a
transmitter tapping the middle of a pipe (a {"junction"} end) reported
connected_to="" and an instrument on untagged equipment fell back to the
signal line's own number — which Task 13 always stamps, so the handle
fallback was unreachable and every untagged mounting was labelled with
its wire. Spec 9.5's "line numbers" clause is exactly the junction case.
_far_ends now names the far node's tag (its handle when untagged) and,
at a junction, the line number of every line the junction joins (that
line's handle when unnumbered). Two tests exercise both mountings.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd
