docs(desktop): document Umbriel package and layout updates

docs/shell/scripts.mdx

@@ -32,6 +32,7 @@ Several scripts below also exist as fish functions of the same name (`ai`, `c2p`
 | --- | --- | --- |
 | [`ai`](#ai) | sh | Pick an AI CLI with gum and launch it |
 | [`atuin-pick`](#atuin-pick) | python3 | atuin history picker for a kitty or tmux split |
+| [`brave-new-tab`](#brave-new-tab) | sh | Open a URL in a new Brave Origin tab |
 | [`c2p`](#c2p) | sh | code2prompt with an fzf-picked template |
 | [`extract_agents`](#extract_agents) | sh | Copy all `AGENTS.md` files into a directory tree |
 | [`fab`](#fab) | sh | fzf picker for Fabric patterns |
@@ -79,6 +80,25 @@ It is written for launch contexts where atuin's shell init never ran. It runs `a
 
 **Needs:** `python3`, `atuin`, `fish`.
 
+## brave-new-tab
+
+```sh
+brave-new-tab <url>
+```
+
+Runs `brave-origin --new-tab <url>` detached with `setsid -f`. With Brave Origin running, the URL opens as a tab in its last active window; otherwise Brave Origin starts with it. Exits 2 unless given exactly one argument.
+
+A URL without a scheme gets one from its host (port and path ignored): `localhost`, `*.localhost`, `*.local`, and `127.*` get `http://`, everything else `https://`. URLs containing `://`, and `about:` URLs, pass through unchanged.
+
+| Argument | Opens |
+| --- | --- |
+| `example.com/path` | `https://example.com/path` |
+| `localhost:3000` | `http://localhost:3000` |
+| `printer.local` | `http://printer.local` |
+| `http://example.com` | `http://example.com` |
+
+**Needs:** `brave-origin` (`brave-origin-bin`), `setsid` (util-linux).
+
 ## c2p
 
 ```sh