UR-Nexus 1.68.3

• Ollama request failed (400): http: request body too large now explains
  itself. That string comes from Go's net/http MaxBytesReader rejecting the
  payload on byte size, which is a different limit from the model's context
  window — so the token-based context warning added in 1.66.2 never fires for
  it, and a couple of screenshots can breach it while the token estimate still
  looks comfortable. The request body is now measured at the send site, and the
  error reports its actual size, names images as the usual cause (base64 adds
  roughly a third, and every image persists in the transcript on later turns),
  offers /compact or a fresh session, and notes that a reverse proxy in front
  of Ollama enforces its own limit (client_max_body_size for nginx) which
  tuning Ollama would not affect.
• The classifier matches the 413 spellings a proxy returns as well as the Go
  400, and is tested against unrelated 400s so it cannot replace a correct error
  with confident, irrelevant advice.