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/remove-instance.sh

@@ -23,7 +23,8 @@ PM2_NAME="autofirmer-$N"
 
 node - "$REGISTRY" "$PM2_NAME" <<'NODE'
 const { readFileSync, writeFileSync } = require('node:fs');
-const [, file, name] = process.argv;
+// `node -` puts '-' in argv[1], so the arguments start at argv[2].
+const [file, name] = process.argv.slice(2);
 const entries = JSON.parse(readFileSync(file, 'utf8'));
 if (!entries.some((e) => e.name === name)) { console.error(`  [X] ${name} is not registered`); process.exit(1); }
 writeFileSync(file, JSON.stringify(entries.filter((e) => e.name !== name), null, 4) + '\n');