- mosaic-task.mjs prune [--keep=N] [--yes]: default keep 50; without
--yes lists candidates without deleting
- only r-* directories under the runs root; symlinks skipped;
sessions/workspaces/state/config untouched (asserted by suite sentinels)
- append-only receipt runs/.pruned.log records every pruned id
- test-task.sh: +8 retention cases (dry-run no-delete, keep-N, newest
kept, receipt, isolation, invalid keep, empty no-op)
Also: suite hardening - prune section scopes its config per-command
(no export/unset leaking into later sections); duplicated check()
removed; latest_reason hoisted to helpers; status colors now green OK /
red FAIL (terminal-only, NO_COLOR-aware) per owner UX feedback.
Closes#32