Add RTL (right-to-left) layout support for Hebrew/Arabic users

Problem

Claude Code's TUI is rendered left-to-right with no way to mirror the
layout. While Hebrew/Arabic text inside messages renders correctly via
the terminal's BiDi handling, the surrounding UI chrome — input box,
status bar, panels, indicators — is locked LTR.

For native RTL-language users this creates a constant context switch
between the conversation content (which flows RTL) and the UI shell
(which flows LTR).

Request

Add an opt-in RTL mode that mirrors the TUI layout:

• Input prompt and cursor anchored to the right
• Status bar / indicators mirrored
• Panels and boxes mirrored
• Keep code blocks and English text LTR within the RTL frame

Could be exposed as a setting ("rtl": true in settings.json) or
auto-detected from LANG / LC_ALL when set to an RTL locale.

Environment

• Claude Code on macOS (Terminal.app / iTerm2)
• Native Hebrew speaker, daily user