Reject backup jobs without paths

docs/book/src/operations/backups-and-restores.md

@@ -6,11 +6,12 @@ Three ways to trigger one:
 
 1. **Scheduled** — the agent's local cron fires at the time set
    on the schedule.
-2. **Run-now** — operator clicks **Run now** on the host detail
-   right rail. Posts to `/hosts/{id}/run-backup` (defaults to all
-   source groups) or to a per-group form for finer control.
-3. **API** — `POST /api/hosts/{id}/jobs` with the appropriate
-   payload. Same audit + dispatch path.
+2. **Run-now** — operator clicks **Run now** for a specific source
+   group. This uses `POST /hosts/{id}/source-groups/{gid}/run`.
+3. **API** — use `POST /api/hosts/{id}/source-groups/{gid}/run` for a
+   configured source group. The lower-level `POST /api/hosts/{id}/jobs`
+   backup form requires explicit paths in `args`; an empty backup is
+   rejected instead of dispatching a job that restic cannot run.
 
 In every case the server creates a `jobs` row, broadcasts a
 `command.run` to the host, and lands the operator on the live