all: support hiding subconvo output

Some of it is systematically noisy.
diff --git a/claudetool/pre-commit.go b/claudetool/pre-commit.go
index 306c7b9..f8fe5a0 100644
--- a/claudetool/pre-commit.go
+++ b/claudetool/pre-commit.go
@@ -55,6 +55,7 @@
 
 	info := conversation.ToolCallInfoFromContext(ctx)
 	sub := info.Convo.SubConvo()
+	sub.Hidden = true
 	sub.PromptCaching = false
 
 	sub.SystemPrompt = `Analyze the provided git commit messages to identify consistent patterns, including but not limited to: