Document Linux and Windows CLI install paths in server-setup

Closes QS-004. The server-setup CLI section only showed the macOS
Homebrew install. Linux operators — the majority — had no way to
follow the docs since the tap only publishes darwin artifacts.

Now shows three install options in order (install.sh for Linux/macOS,
brew tap for macOS, install.ps1 for Windows) and links to the
platform-detecting installer on the CLI page.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: durable-workflow-ops

docs/server-setup.md

@@ -263,9 +263,15 @@ See the [server README](https://github.com/durable-workflow/server#getting-start
 The [Durable Workflow CLI](/docs/2.0/cli) provides a shell interface to the server:
 
 ```bash
-# Install
+# Install — Linux and macOS
+curl -fsSL https://durable-workflow.com/install.sh | sh
+
+# Install — macOS (Homebrew alternative)
 brew install durable-workflow/tap/dw
 
+# Install — Windows (PowerShell)
+# irm https://durable-workflow.com/install.ps1 | iex
+
 # Configure
 export DURABLE_WORKFLOW_SERVER_URL=http://localhost:8080
 export DURABLE_WORKFLOW_AUTH_TOKEN=your-token
@@ -277,6 +283,8 @@ dw workflow:list
 dw workflow:start --type=my-workflow --input='{"key":"value"}'
 ```
 
+See the [CLI install page](/docs/2.0/cli#install) for a platform-detecting installer and direct binary downloads.
+
 ## Deployment
 
 ### Docker