docs: restore the blank line before the first environment

Shortening Layout consumed the blank line that separated it from ## Crawler.

README.md

@@ -76,6 +76,7 @@ policies, with the calibrated temperature bands in its own README.
 Each build is **model-removed**: no policy is baked in — supply one at run time
 (the stock policy here, or the Causal GPT-RL policy from the model repo). All
 launch headless.
+
 ## Crawler
 
 - Scene: **10 agents**, observation **158**-d (sensor channels `126 + 32`), action