pxx 2.4.4

Changed

• Review prompt: severity discipline to stop small reviewers over-flagging. The review gate's
  system prompt (pxx/prompts/review.md) told the model to APPROVE only with "no high or medium
  findings" but never that style, comments, renames, test-only edits, import order, and refactors
  that keep tests green are not defects — so smaller judges rated acceptable-change nitpicks as
  medium and voted REVISE. Added an explicit rule reserving high/medium for real correctness
  or safety defects; minor/stylistic observations are low at most and never a reason to REVISE.
  Measured on the calibration corpus at temperature:0: qwen2.5-coder:32b false-positive rate
  0.429 → 0.143 (now passes calibration ok) and qwen2.5:14b-instruct 0.429 → 0.286,
  with recall unchanged at 0.857 (precision up, no loss of critical-bug detection). This makes
  a fast, GPU-resident local model a viable blocking reviewer. NOTE: the calibration corpus is
  small (14 cases) — treat the magnitude as indicative pending held-out validation on real diffs.