claudetool: add simplified patch support

For weaker models.

Also, improve fallback parsing introduced earlier.
diff --git a/llm/ant/ant.go b/llm/ant/ant.go
index 046456f..7be2911 100644
--- a/llm/ant/ant.go
+++ b/llm/ant/ant.go
@@ -565,3 +565,8 @@
 		}
 	}
 }
+
+// For debugging only, Claude can definitely handle the full patch tool.
+// func (s *Service) UseSimplifiedPatch() bool {
+// 	return true
+// }