Adds claude/settings.json to the repo and maps it in .dotter/global.toml
so Claude Code settings (including attribution.sessionUrl = false, which
disables the session link in commit trailers and PR descriptions) are
version-controlled and deployed as a symlink like CLAUDE.md.
Claude-Session: https://claude.ai/code/session_01RyUSWPV85RTPNY4H66Jnkw
