feat: add createOpencodeTui() function to SDK for programmatic TUI launching

[ScriptedAlchemy]

This PR adds a new createOpencodeTui() function to the JavaScript SDK that allows programmatic launching of the opencode TUI interface.

Changes

• Added TuiOptions type with optional project, model, session, and agent parameters
• Added createOpencodeTui() function that spawns the opencode TUI process with inherited stdio
• Function takes over the current terminal for interactive TUI experience

Usage

import { createOpencodeTui } from '@opencode/sdk'

const tui = createOpencodeTui({
  project: '/path/to/project',
  model: 'claude-3-5-sonnet',
  session: 'session-id',
  agent: 'agent-name'
})

The TUI will launch and take over the current terminal, providing an interactive coding experience.