feat(goose-cli): add TUI status bar and goose ASCII splash screen

[balcsida]

Summary

Add a terminal UI (TUI) mode to the Goose CLI with:

• Goose ASCII art splash screen — displays a standing goose with a speech bubble showing version, model/provider, and working directory on startup
• Persistent 2-line status bar — pinned to the bottom of the terminal using scroll region management, showing model, project, git branch, token usage, mode, extensions, and cost
• Swimming goose turn separator — replaces the plain text separator while the assistant is processing
• --no-tui flag — disables all TUI features for piped/scripted usage
• Hidden goose honk easter egg — prints a knife-wielding goose and exits

Splash screen

       ,--.        
      ( o  )>      ╭───────────────────────╮
      /   /        │  Goose v1.24.0        │
     /   /         │  haiku-4.5 · litellm  │
    /   /____      │  ~/github.com/goose   │
   (         )     ╰───────────────────────╯
    \_______/      
      ||  ||       
      ^^  ^^       

Type of Change

• Feature
• Bug fix
• Refactor / Code quality
• Performance improvement
• Documentation
• Tests
• Security fix
• Build / Release
• Other (specify below)

AI Assistance

• This PR was created or reviewed with AI assistance

Testing

• cargo build -p goose-cli --bin goose compiles without warnings
• cargo test -p goose-cli — all 148 tests pass
• Manual testing of goose session with TUI enabled: splash, separator, and status bar render correctly
• Manual testing of goose session --no-tui: original text greeting, no status bar
• Manual testing of goose honk: prints knife goose and exits
• Terminal resize re-renders the status bar correctly

Related Issues

Builds on the ASCII art from #7329

Screenshots/Demos (for UX changes)

Before: Plain text greeting with no status bar

After: Goose ASCII splash + persistent status bar (screenshots to be added after merge testing)