Two reader defects, both about trusting a derived number over the drawing.
Stale junctions: endpoints were resolved before a foreign line's membership
was decided, so a P&ID line ending on a foreign line that was then discarded
(it touched no node) kept `{"junction": "J1"}` while `junctions` was empty
and `stats.dangling` was one short. Node attachment now runs first for every
edge, the foreign lines that attach are admitted, and only then are junctions
and dangling ends resolved over the edges actually in the graph.
Chord length: `length` was a chord walk over the vertices, 12.5% short on a
semicircular crossing jump with no field saying so, and junction detection
tested the chord too, so a line ending on the arc dangled. Both engines now
report per-vertex `bulges` next to `points` (COM asks GetBulge only when
`Length` exceeds the chord walk, since an arc is always longer than its
chord); the reader takes the engine's bulge-aware `length` and tests
endpoints against the arc. The chord sum survives only for an engine that
reports no length, and is then labelled `length_approximate`.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd
