DEPLOY.md: pre-create ~/SDP/data on 186; create it in step 6a too

The control plane binary will create the data dir on first
start, but doing it before systemd starts the service means
the ReadWritePaths scope has somewhere to point at, and
faster diagnosis if anything else is wrong.

DEPLOY.md

@@ -94,6 +94,14 @@ ssh administrator@172.18.136.92 "chmod +x ~/SDP/bin/agent-micro"
 ssh administrator@172.18.139.186 "chmod +x ~/SDP/bin/control-plane ~/SDP/bin/agent-gateway"
 ```
 
+**Pre-create the control plane's data dir on 186** (SQLite + log files live here):
+
+```bash
+ssh administrator@172.18.139.186 "mkdir -p ~/SDP/data && ls -ld ~/SDP/data"
+```
+
+Should print `drwxr-xr-x ... administrator administrator ... /home/administrator/SDP/data`. The control plane binary creates it on first run too, but doing it now means the systemd unit's `ReadWritePaths` check has somewhere to point at.
+
 ## 5. Push the systemd unit files
 
 From your laptop. `scp` will prompt for the password.
@@ -123,8 +131,9 @@ Status should be `active (running)`. Journal should show a clean startup, then e
 ### 8b. 186 (control plane FIRST, then gateway agent)
 
 ```bash
-ssh administrator@172.18.139.186
 sudo install -m 644 -o root -g root /tmp/sdp-control-plane.service /etc/systemd/system/sdp-control-plane.service
+sudo mkdir -p /home/administrator/SDP/data
+sudo chown administrator:administrator /home/administrator/SDP/data
 sudo systemctl daemon-reload
 sudo systemctl enable sdp-control-plane.service
 sudo systemctl restart sdp-control-plane.service