feat: 1 basic chatting interface

[chengus]

Problems!

Janky outlines, need to resize terminal once to fix it

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This pull request integrates OpenRouter chat functionality into the TUI app, enabling users to interact with language models directly from the terminal interface. It introduces a new chat UI, handles streaming responses, manages keyboard shortcuts for navigation and shutdown, and displays model and token usage information.

OpenRouter integration and chat functionality:

• Added @openrouter/sdk as a dependency in package.json and imported it into the app, enabling communication with the OpenRouter API. [1] [2]
• Implemented message sending, streaming response handling, and error management using OpenRouter, including environment variable-based API key retrieval and model selection.

User interface and experience improvements:

• Redesigned the UI to display chat history in a scrollable box, show model information, reasoning token usage, and error messages, and provide an input box for user messages.
• Added keyboard shortcuts for scrolling (PgUp/PgDn, Ctrl+U/Ctrl+D) and quitting (Esc/Ctrl+C), enhancing usability in the terminal.

App lifecycle management:

• Introduced proper shutdown handling to abort in-progress requests and exit cleanly on quit commands or renderer destruction.