docs: add macOS install instructions for CLI

Add a tabbed platform selector (Linux/macOS) to the CLI install page.
The macOS tab downloads the aarch64-darwin binary and includes a note
about the Gatekeeper quarantine workaround for browser downloads.

Signed-off-by: Spyros Seimenis <sse@edgeless.systems>

Author: sespiros

docs/docs/howto/install-cli.md

@@ -12,14 +12,33 @@ Required for deploying with Contrast.
 
 ## How-to
 
-Download the Contrast CLI from the latest release:
+Download the Contrast CLI from the latest release and install it in your PATH:
+
+<Tabs queryString="platform">
+<TabItem value="linux" label="Linux (x86_64)">
 
 ```bash
-curl --proto '=https' --tlsv1.2 -fLo contrast https://github.com/edgelesssys/contrast/releases/latest/download/contrast
+curl --proto '=https' --tlsv1.2 -fLo contrast https://github.com/edgelesssys/contrast/releases/latest/download/contrast-x86_64-linux
+sudo install contrast /usr/local/bin/contrast
 ```
 
-After that, install the Contrast CLI in your PATH, e.g.:
+</TabItem>
+<TabItem value="macos" label="macOS (Apple Silicon)">
 
 ```bash
+curl --proto '=https' --tlsv1.2 -fLo contrast https://github.com/edgelesssys/contrast/releases/latest/download/contrast-aarch64-darwin
 sudo install contrast /usr/local/bin/contrast
 ```
+
+:::note
+If you download the binary via a web browser instead of `curl`, macOS may show a warning
+that the software can't be verified. Remove the quarantine attribute to resolve this:
+
+```bash
+xattr -d com.apple.quarantine contrast
+```
+
+:::
+
+</TabItem>
+</Tabs>