Instance scripts: read node - arguments from argv[2]

`node -` puts '-' in argv[1], so the registry snippets in add-instance.sh
and remove-instance.sh were one slot off: they wrote the registry to a file
named "-" in the working directory, with the instances.json path as the
instance name, a null port and the port as the db. scripts/instances.json
was never created, so the updater and start-all only ever knew instance 1 —
after an update, instance 2 and up kept running old code against the new
build until someone ran `pm2 restart all`.

Devices that already ran add-instance.sh need their scripts/instances.json
written by hand (and the stray "-" file deleted).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scripts/add-instance.sh

@@ -68,7 +68,8 @@ command -v pm2 >/dev/null 2>&1 || die "PM2 not installed - run install-autostart
 # ── registry: create with the legacy entry, refuse duplicates, append ───────
 node - "$REGISTRY" "$PM2_NAME" "$PORT" "$DB_REL" <<'NODE'
 const { existsSync, readFileSync, writeFileSync } = require('node:fs');
-const [, file, name, port, db] = process.argv;
+// `node -` puts '-' in argv[1], so the arguments start at argv[2].
+const [file, name, port, db] = process.argv.slice(2);
 const entries = existsSync(file)
     ? JSON.parse(readFileSync(file, 'utf8'))
     : [{ name: 'autofirmer', port: 3000, db: 'autotrader.sqlite' }];