Adds /theme, /voice, /sandbox-toggle (alias /sandbox), /keybindings,
and /btw ported from npm src/commands/. Settings-touching commands
write through the existing ConfigRuntime to .claude/settings.local.json
(theme, voiceEnabled, sandbox.excludedCommands). /keybindings creates
a JSON template on first invocation. /btw flips into a prompt-style
result that asks the model to answer the side question without
mutating workspace state.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>