Pin harness to 60a6e81 (comma-separate adjacent citations)

Two citations on the same word were rendering as a single big number
(¹⁰¹¹¹²); the new harness inserts commas at citation boundaries so
they read as ¹⁰,¹¹,¹².

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

requirements.txt

@@ -1,6 +1,6 @@
 click>=8.1
 litellm @ git+https://github.com/BerriAI/litellm.git@d251238
-a-simple-llm-harness @ git+https://github.com/chuckfinca/a-simple-llm-harness.git@99fc607
+a-simple-llm-harness @ git+https://github.com/chuckfinca/a-simple-llm-harness.git@60a6e81
 e2b-code-interpreter>=2.5
 huggingface-hub
 python-dotenv