chore: curate plugin usage rules

Sync AGENTS.md from a focused UsageRules config that includes Tribes and tribes_plugin_api guidance for plugin authors. Keep Ash deep rules linked to reduce context size and make scripts/plugin executable so the documented workflow works directly.

mix.exs

@@ -55,7 +55,21 @@ defmodule MyPlugin.MixProject do
   defp usage_rules do
     [
       file: "AGENTS.md",
-      usage_rules: [:elixir, :otp, :phoenix, ~r/^phoenix_/, :ash]
+      usage_rules: [
+        {:usage_rules, sub_rules: []},
+        {"usage_rules:elixir", main: false},
+        {"usage_rules:otp", main: false},
+        "phoenix:ecto",
+        "phoenix:html",
+        "phoenix:liveview",
+        "phoenix:phoenix",
+        {:ash, sub_rules: []},
+        {"ash:actions", link: :markdown, main: false},
+        {"ash:migrations", link: :markdown, main: false},
+        {"ash:testing", link: :markdown, main: false},
+        {:tribes_plugin_api, sub_rules: []},
+        {:tribes, sub_rules: []}
+      ]
     ]
   end