Release v2.11.3

Fixed

• A ring cure handed its last batch of rings to postcure unrelaxed. Every batch
  but the last is relaxed twice: once by the per-iteration relax as soon as its bonds
  exist, and again by the next iteration's closure ladder, which is eight
  minimizations and 16 ps at 600 K against the relax's one minimization and 4 ps at
  300 K. The final batch only ever gets the first, and then goes straight into a
  500 K anneal.

  htpolynet-study measured it on three 2.11.1 builds, all of which had ended on a
  ring-forming iteration and had therefore been relaxed. Bond energy entering the
  anneal tracked how many rings that last iteration formed -- 1, 1 and 4 rings for
  18849, 26113 and 35959 kJ/mol, against 13619 +/- 226 for a route that enters already
  relaxed. An inventory of one such structure found five bonds beyond 2.0 A: one
  triazine's three ring bonds at 2.24 A, and two monomers whose own backbones the
  ladder had stretched to 2.34 and 3.20 A while pulling their arms toward different
  rings. Eleven of twenty builds died in the anneal.

  The cure now runs a minimization and a short 300 K NVT once on exit, mirroring what
  the postcure repair stage already did for the route that never saw this. It is
  unconditional -- the cure has four ways to end and which of them leaves strain behind
  is not worth reasoning about per exit -- and configurable as ring_cure.settle.

  Confirmed paired, same eight velocity seeds against the same two structures on the
  same hardware: two anneals exploded without the settle and none with it. The two
  came from different source structures, one of which had never failed in production,
  so the effect is not particular to a pathological build, and nothing exploded during
  the settle itself -- the minimization absorbs the strain rather than the failure
  moving earlier. Eight seeds is a small sample and that comparison alone would be
  weak; it is corroboration of the bond energies above, not the case on its own.