fix: keep command-line debug session-only

frontend/tests/debug-mode-test.mjs

@@ -0,0 +1,32 @@
+import assert from 'node:assert/strict';
+import fs from 'node:fs';
+import path from 'node:path';
+import vm from 'node:vm';
+
+const source = fs.readFileSync(path.resolve('frontend/src/lib/log/debug.js'), 'utf8');
+const values = new Map();
+const localStorage = {
+  getItem(key) { return values.has(key) ? values.get(key) : null; },
+  setItem(key, value) { values.set(key, String(value)); },
+  removeItem(key) { values.delete(key); },
+};
+const context = vm.createContext({
+  console: { log() {} },
+  localStorage,
+  window: { location: { search: '' } },
+});
+const module = new vm.SourceTextModule(source, { context, identifier: 'debug.js' });
+await module.link(() => { throw new Error('debug.js must not import modules'); });
+await module.evaluate();
+
+const { debug } = module.namespace;
+debug.enable({ persist: false });
+
+assert.equal(debug.isEnabled(), true, 'session debug should enable diagnostics');
+assert.equal(
+  localStorage.getItem('verstak-debug'),
+  null,
+  'a --debug session must not make diagnostics persist into ordinary launches',
+);
+
+console.log('debug mode smoke passed');