Phase 7a: use the n8n SSH node (Execute Command is disabled in n8n 2.x)

n8n 2.x disables n8n-nodes-base.executeCommand by default (nodes.exclude), so the
first workflow shape could not activate: 'Unrecognized node type'. Replace the
Execute Command node with the SSH node, which is enabled, and keep the restricted
trigger key: the server forced command runs exactly scripts/morning-brief.sh.

- deploy/n8n-morning-brief.json: schedule + optional manual trigger -> SSH node
  -> Code check that makes a non-zero exit red (FR-12).
- deploy/import-n8n-morning-brief.sh: builds the sshPrivateKey credential from the
  key (id schoolScanKey, mode-0600 temp, removed after import), imports, publishes,
  restarts once, and confirms activation in the n8n log.
- scripts/morning-brief.sh: default IMAGE 0.6.1-phase8 so the scheduled job uses
  the deployed image.
- docs/phase-7a-n8n-schedule.md, deploy/DEPLOYMENT.md: document the design and the
  throwaway-n8n rehearsal (activation + success + failure path).

deploy/DEPLOYMENT.md

@@ -100,12 +100,15 @@ the API directly on the internal address.
 
    ```bash
    deploy/setup-n8n-scan-key.sh --apply      # restricted SSH key for the trigger
-   deploy/import-n8n-morning-brief.sh --apply # import + publish + restart n8n
+   deploy/import-n8n-morning-brief.sh --apply # credential + workflow + publish + restart n8n
    ```
 
-   The workflow has one Execute Command node: `ssh … 'scripts/morning-brief.sh'`.
-   It needs no `SCHOOL_NOTIFY_TOKEN` in n8n — the host script reads the project env
-   file. See `docs/phase-7a-n8n-schedule.md` for the design and the failure drill.
+   The workflow is Schedule Trigger -> SSH node -> a Code check that makes a
+   non-zero exit red. The SSH node authenticates with the restricted key and runs
+   `scripts/morning-brief.sh` on the host. (n8n 2.x disables the Execute Command
+   node by default, so a command node cannot activate.) It needs no
+   `SCHOOL_NOTIFY_TOKEN` in n8n — the host script reads the project env file. See
+   `docs/phase-7a-n8n-schedule.md` for the design and the failure drill.
 
 Notes:
 
@@ -120,4 +123,6 @@ Notes:
 - The 06:00 schedule is the n8n workflow `Compass / NHS — 6:00am morning brief`
   (`deploy/n8n-morning-brief.json`), triggered over a restricted SSH key. It runs
   on the shared n8n service on `.13`, so its import, publish, and the one-off n8n
-  restart need approval first.
+  restart need approval first. n8n 2.x disables the Execute Command node by default,
+  so the workflow uses the SSH node plus a Code check that fails the run on a
+  non-zero exit.