Release v2.11.6

Added

• A ring cure now refuses a closure that threads a ring already present, and registers
  the rings it makes. Two halves of one gap.

  reject_threaded_rings, added in 2.11.4, asks whether a new ring would close around
  an existing bond. It does not ask the converse --- whether dragging three monomers
  together has run one of their bonds through a ring that was already there. Over ten
  builds htpolynet-study found that second kind is mostly phenyls, which outnumber
  triazines about six to one here, and that two of three were made by the cure rather
  than by packing: one appeared in the same iteration as a triazine piercing, which is
  what identifies the two as a single event. reject_new_threading closes it.

  Only threadings the ladder creates count. The participating monomers are surveyed
  before the closure ladder and again after it, so a monomer that arrived from packing
  already threaded is not silently refused every reaction for the rest of the build ---
  one of those exists in their data.

  The second half is that Topology.rings never contained a cure-formed ring.
  detect_rings() runs once per molecule template and the list is replicated at system
  build; nothing updated it afterwards, and the product splice did not register the
  triazine it creates. So every ring the ring cure ever made was invisible to every
  ring-aware check in htpolynet --- including CURE's own pierces_ring, which means a
  pairwise crosslink could thread a previously formed triazine with nothing noticing.
  form_rings now registers each ring as it makes it.

  No evidence yet that threading of either kind measurably affects Tg or density; the
  case for both filters is mechanism, not measured harm. Set
  ring_cure.reject_new_threading: false to reproduce the old behavior.

Changed

• The box and density figures in the 2.11.5 and 2.11.4 notes below are retracted.
  Both releases quote traces --- +27.9% in volume, path 0.4104 nm, a two-regime
  expansion and contraction --- produced by relax and equilibrate running against
  the ladder topology, which is the defect 2.11.5 fixes. The box was responding to a
  restrained, unbonded system, so those numbers describe nothing real and should not be
  requoted. They are left in place rather than rewritten, because the releases went out
  with them.

  What survives unaffected: conversion, ring counts and iteration counts, which are
  decided before those stages run; the threading filter's validation; the constant-volume
  control, since NVT cannot move the box whatever topology it reads; and every
  measurement from the pairwise route, which writes its topology correctly.