Enhancement: add --doctor CLI diagnostic flag

[oscarpeer-design]

Describe the changes you have made:

This PR introduces a --doctor CLI flag to the terminal interface, allowing users to run a full environment diagnostics check directly from the command line.

When invoked, the doctor system performs a sequence of runtime checks on the current environment using run_doctor(OpenInterpreter()), including:

• Python runtime information
• Required package availability
• Environment variable configuration (API keys)
• Model/provider resolution via LiteLLM
• File system and shell execution permissions
• Optional CUDA/GPU availability

How it runs:

When the CLI is executed with the --doctor flag
python -m interpreter.terminal_interface.start_terminal_interface --doctor

The terminal interface:

• Parses CLI arguments on startup
• Detects the --doctor flag
• Instantiates a clean OpenInterpreter instance
• Calls run_doctor(OpenInterpreter())
• prints diagnostic results to stdout and exits after completion.

Behavioural verification:

• Doctor runs end-to-end and prints full diagnostic report
• CLI correctly triggers doctor execution when --doctor is provided
• No changes to interpreter runtime behaviour outside CLI diagnostic mode

Reference any relevant issues (e.g. "Fixes #000"):

This feature was introduced as part of internal CLI tooling improvements and does not reference a tracked issue.

Pre-Submission Checklist (optional but appreciated):

• I have included relevant documentation updates (stored in /docs)
• I have read docs/CONTRIBUTING.md
• I have read docs/ROADMAP.md

OS Tests (optional but appreciated):

• Tested on Windows (correctly outputs diagnosis based on user environment and installed models)
• Tested on MacOS
• Tested on Linux

[endolith]

This is for troubleshooting local LLMs?