Add gitignore to exclude sisyphus directory files

oh-my-opencode excludes the sisyphus working directory in their own repo, so it seems to be best practice. Also, the directory captures agent/runtime state, so it should not be shared.

Author: malheleco

OhMyOpenCode.gitignore

@@ -0,0 +1,2 @@
+.sisyphus/*
+!.sisyphus/rules/