Running history per plugin and host class, used to promote or demote a verdict #157

Companion of the plugin-hostd grouping planner (operator priority 2026-10-27): the host records what each plugin did on this machine (CPU, xruns, worker restarts, crashes); plugin-qualify reads that history and moves a verdict (in-process / isolated / refused) when the record disagrees with the measurement. Same plugin, different host class, different history.