v0.4.0

• update command — fetch latest version and re-register (claudewatch update)
• version command — print installed version (claudewatch version)
• /claudewatch:update skill for updating via Claude Code
• Install now creates config file with all keys explicitly set
• show_cost defaults to false (was true)
• Uninstall preserves config file for future reinstalls
• /claudewatch:config skill now covers all settings — theme + all segment toggles