feat: implement TUI client for terminal-based interaction

[vanducng]

Summary

Build a Terminal User Interface (TUI) client as an alternative way to interact with GoClaw directly from the terminal, complementing the existing Web UI and messaging channels.

Context

GoClaw currently offers a Web UI (ui/web/) and messaging channel integrations (Telegram, Discord, etc.). A TUI would provide a native terminal experience for developers and power users who prefer staying in the terminal — ideal for SSH sessions, headless environments, and quick interactions without opening a browser.

Scope

• Research TUI frameworks — Go-based (Bubble Tea, tview) or TypeScript-based (Ink, blessed) with Bun runtime
• Place under ui/tui/ alongside the existing ui/web/
• Connect to GoClaw via WebSocket (reuse existing protocol v3) or HTTP API
• Core features: agent chat, session management, basic config viewing
• Integrate as a CLI subcommand (e.g., goclaw tui) or standalone TUI binary

Acceptance Criteria

• TUI app lives in ui/tui/
• Connects to a running GoClaw instance (managed mode)
• Supports sending messages and receiving streamed responses
• Registered as a goclaw tui subcommand in cmd/ or runnable standalone

Assignee

@vanducng