feat: support /config and dictation language in Remote Control sessions

Problem

When using Claude Code via Remote Control (CLI on a remote Linux server, connecting from a Mac browser/app), the /config command is unavailable — it returns "/config isn't available over Remote Control."

This means there's no way to change the voice dictation language from the Remote Control client. The language setting in ~/.claude/settings.json on the server is set to Portuguese, but the speech-to-text in the Remote Control client defaults to English with no way to override it.

Expected behavior

• /config should work in Remote Control sessions (at least for client-side settings like dictation language), OR
• The Remote Control client should read the server's language setting and apply it to dictation, OR
• There should be a client-side setting in the Remote Control UI to configure dictation language

Reproduction

1. SSH into a Linux server, cd to a project
2. Run claude remote-control
3. Connect from Mac via claude.ai/code
4. Try /config → "not available over Remote Control"
5. Try /voice → dictation defaults to English, no way to change