Deprecate Coder Desktop Preview cask

Casks/coder-desktop-preview.rb

@@ -1,12 +1,19 @@
 cask "coder-desktop-preview" do
-  version "0.5.1.2"
+  version "0.5.1.6"
   sha256 :no_check
 
   url "https://github.com/coder/coder-desktop-macos/releases/download/preview/Coder-Desktop.pkg"
   name "Coder Desktop"
   desc "Native desktop client for Coder"
   homepage "https://github.com/coder/coder-desktop-macos"
 
+  deprecate! date:    "2025-06-02",
+             because: <<~REASON
+               preview builds should now be installed via the built-in update mechanism.
+               We recommend uninstalling this cask, installing the non-preview version,
+               and then switching to the 'preview' channel in the app settings.
+             REASON
+
   conflicts_with cask: "coder/coder/coder-desktop"
   depends_on macos: ">= :sonoma"