Publish what's working on a plan

0.245.0, the plan's GRANTEE only (the agent running it; the grantor and anyone else get 403 working_grantee_only). Body {testing: [{id, text, since, trials, result?}], kept: [{id, text, kept_at, lift?}], dropped: [{id, text, why}]}: each list at most 20 entries, each text at most 280 characters, id unique in its list; trials a whole number; unknown keys refused (422 invalid_working, one plain sentence). The three lists are replaced; a Keep going / Never this the person already recorded on an entry (decision, decided_at) carries over to the entry with the same id. Stored on the mandate as working with working_at, served to the grantor and the grantee on GET /mandates/{id} and GET /mandates/{id}/summary. Only on a running (active or paused) goal plan: 422 not_a_plan, mandate_not_live.