Phase 7a: stable workflow id for the n8n import (AUD-115)

n8n 2.18.5 rejects an import whose workflow JSON has no `id`
(SQLITE_CONSTRAINT: NOT NULL constraint failed: workflow_entity.id). Give the
workflow a fixed id and record that the import -> publish -> active flow was
rehearsed in a throwaway n8n container before asking for approval.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

deploy/n8n-morning-brief.json

@@ -1,4 +1,5 @@
 {
+  "id": "schoolMorningBrf",
   "name": "Compass / NHS — 6:00am morning brief",
   "nodes": [
     {

docs/phase-7a-n8n-schedule.md

@@ -70,6 +70,16 @@ The script copies the JSON into the container with `docker exec -i … sh -c 'ca
 `update:workflow --active`), restarts n8n once so the 06:00 schedule registers, and
 prints `n8n list:workflow --active=true`.
 
+The JSON carries a stable `id` (`schoolMorningBrf`). n8n 2.18.5 refuses an import
+whose workflow has no `id` (`SQLITE_CONSTRAINT: NOT NULL constraint failed:
+workflow_entity.id`), so the id is required, not cosmetic. Re-importing the same file
+updates the same workflow instead of adding a second copy.
+
+`n8n publish:workflow` prints *"Changes will not take effect if n8n is running"*, which
+is why the import script restarts n8n once. The full import → publish → active check
+was rehearsed in a throwaway n8n container with a temporary data directory before this
+plan was proposed; no shared instance was touched.
+
 ## Verification
 
 ```bash