docs(ide): document "IndexedDB database 'vscode-web-db' is closed" error

src/content/docs/guides/ide.md

@@ -16,3 +16,25 @@ You can open these docs as a webview in the IDE. Open the command palette
 (`cmd/ctrl+shift+p`) and type `Open docs`.
 
 :::
+
+## Troubleshooting
+
+### "IndexedDB database 'vscode-web-db' is closed"
+
+The IDE stores its local state (logs, editor state, unsaved changes) in your
+browser's IndexedDB. If that database connection is closed while the IDE is
+still running, you may see errors such as
+`Unable to write file 'vscode-log:/…/window.log' (Error: IndexedDB database 'vscode-web-db' is closed.)`.
+
+This usually happens when:
+
+- The IDE is open in more than one tab and one of them loads a new version,
+  which closes the database in the other tabs.
+- Browser site data for `ide.membrane.io` was cleared (manually or by the
+  browser evicting storage) while the IDE was open.
+- The browser is in private/incognito mode, where storage can be discarded at
+  any time.
+
+Reloading the tab reconnects to the database and resolves the error. To avoid
+it, keep a single IDE tab open per browser profile and reload after clearing
+site data.