Call it a node pack, not a plugin

"Plugin" is not ComfyUI's vocabulary. What Manager installs into custom_nodes/
is a custom node pack, and what the Registry publishes is a "node" — so to
someone browsing the Registry, "plugin" reads slightly off-ecosystem, like
calling a VS Code extension an add-on. The README is the listing page, so the
wording is user-facing.

Replaces the eight occurrences with "node pack", "the nodes", or "this pack" as
each sentence reads best. "Extension" stays reserved for its narrow ComfyUI
meaning: the frontend JS registered via app.registerExtension, which is
web/styleref.js and nothing else.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

tests/test_auth.py

@@ -52,7 +52,7 @@ def test_credentials_path_prefers_xdg():
 
 
 def test_credentials_path_matches_the_cli_default():
-    """CLI and plugin must share one file, or signing in twice becomes necessary."""
+    """CLI and nodes must share one file, or signing in twice becomes necessary."""
     path = auth.credentials_path({"HOME": "/home/u"})
     assert path == os.path.join("/home/u", ".config", "styleref", "credentials.json")