inspect: stop default judge prompts from padding reports

The default profile ships a single judge, and the synthesis prompt mandated a fixed six-section report with no length cap and no omit-empty rule, so even small/clean changes produced long documents padded with 'none' filler under every header.

Rework the judge and chair instructions to lead with a one-line verdict, include a section only when it has real content, and stay proportional to the change without inventing findings to fill a template. The section keywords (Common/Unique findings, Disagreements, Priority order) are retained where relevant; the per-judge panel appendix (multi-judge only) is unchanged.