Delete a scout config

Delete one scout config by its id, removing the per-(team, skill) schedule/emit row outright. The point is cleaning up an orphaned config whose skill was archived or deleted — it lingers in list with an empty description, never runs (the coordinator skips it and the skill can't load), but can't otherwise be removed over the API. Deletion is activity-logged. Note: auto-registration only scans live signals-scout-* skills, so a config deleted for one of those is back on the coordinator's next tick. A scout under any other name does not come back on its own: its config stays deleted until you re-register it, and its skill still reads as a scout meanwhile. To retire a live scout, archive its skill (or set enabled=false to make it inert) rather than deleting the config. A scout whose scout_role is operational cannot be deleted: it is part of the self-driving system rather than the project's own fleet.