fix: allocate share-link layer tokens without collisions

scripts/next-layer-state-token.mjs

@@ -0,0 +1,22 @@
+#!/usr/bin/env node
+
+import {
+  LAYER_STATE_TOKEN_RESERVATIONS,
+  nextLayerStateToken,
+} from '../src/data/layerState.js';
+
+const layerId = String(process.argv[2] || '').trim();
+
+if (!/^[a-z0-9-]+$/.test(layerId)) {
+  console.error('Usage: npm run layer-token:next -- <layer-id>');
+  process.exitCode = 1;
+} else if (Object.hasOwn(LAYER_STATE_TOKEN_RESERVATIONS, layerId)) {
+  console.error(
+    `${layerId} already owns token ${LAYER_STATE_TOKEN_RESERVATIONS[layerId]}`,
+  );
+  process.exitCode = 1;
+} else {
+  console.log(`${layerId}: ${nextLayerStateToken()}`);
+  console.log('Order: free digits 0-9, then two-character base-36 00-zz.');
+  console.log('Re-run after rebasing onto the latest main before merge.');
+}