L7 history: 'adjust --history' promotes or demotes a verdict per host class #158

Lane L7. Needs L1. Reads the history file, writes a second verdict beside the measured one with a reason code, a history block in the record, --pins writes the adjusted verdict when --history is given. Never lifts an rt-safety, feature or unknown verdict; never promotes refused.

Design: https://github.com/FreeMixer/plugin-hostd/blob/main/docs/design/notes/2026-10-27-grouping-planner.md (PR FreeMixer/plugin-hostd#183). Part of FreeMixer/plugin-hostd#182, #157, FreeMixer/openmixer#2263. Operator priority 2026-10-27. One repo, one small change, with its test and the sabotage that reds it.