docs: record autonomous commit preference

Make the repository guidance explicit that agents should commit completed
changes without requesting confirmation.

Test Plan:
- `just fmt` -- passed on the full worktree, including Markdown checks.
- `git diff --cached --check` -- passed.

CLAUDE.md

@@ -4,6 +4,10 @@ Peer-to-peer game library sharing for LAN parties. Peers discover each other on
 the local network via mDNS, exchange library metadata over QUIC, and let users
 browse and download games from each other. Ships as a Tauri desktop app.
 
+## Git
+
+Always commit changes without asking me.
+
 ## Workspace layout
 
 Cargo workspace under `crates/`: