document the phase 2 slice, add ktlint to ci, and warm the gradle cache

tools/preview_server.py

@@ -42,6 +42,10 @@ class Handler(http.server.SimpleHTTPRequestHandler):
     def __init__(self, *args, **kwargs):
         super().__init__(*args, directory=ROOT, **kwargs)
 
+    def end_headers(self):
+        self.send_header("Cache-Control", "no-store, max-age=0")
+        super().end_headers()
+
     def do_GET(self):
         path = self.translate_path(self.path)
         if os.path.isdir(path):