Clarify backend choice and chromium update usage in README

README.md

@@ -221,6 +221,11 @@ Deskify supports two backend modes:
 
 If a site does not work in the default `tauri` backend, try `--backend chromium`.
 
+Quick decision rule:
+
+- Start with the default `tauri` backend for small wrappers and native Linux integration.
+- If the site fails to load, behaves incorrectly, or needs a newer browser engine, rebuild/update with `--backend chromium`.
+
 #### Advanced Build Options
 ```bash
 deskify build \
@@ -337,6 +342,12 @@ deskify update chat --url "https://chat.com" --dry-run
 deskify update chat --url "https://chat.com" --print-config
 ```
 
+Switch an existing app to Chromium compatibility mode while keeping the same internal ID:
+
+```bash
+deskify update chat --url "https://chat.com" --name "Chat" --backend chromium
+```
+
 ### Diagnostics (`doctor`)
 
 Check local prerequisites and common environment issues (Rust/Cargo, `cargo tauri`, `pkg-config`, directories):