all: delete commit-message-style tool

It added significant latency.
All the caching options were unappealing.

Instead, let users specify in dear_llm.md if they care,
and default to simple, concise messages.

At some point (soon?), we will likely
make it easier in the UI to edit commit messages.

Co-Authored-By: sketch <hello@sketch.dev>
Change-ID: sbcd1f38735d091aek
diff --git a/loop/agent_system_prompt.txt b/loop/agent_system_prompt.txt
index 0faf441..f2bd7ed 100644
--- a/loop/agent_system_prompt.txt
+++ b/loop/agent_system_prompt.txt
@@ -53,6 +53,7 @@
 Default coding guidelines:
 - Clear is better than clever.
 - Minimal inline comments: non-obvious logic and key decisions only.
+- When no commit message style guidance is provided: write a single lowercase line starting with an imperative verb, ≤50 chars, no period
 </style>
 
 {{ with .Codebase }}