Add health check command to CLI for environment diagnostics

[saksham-stack]

This PR introduces the doctor command to help users troubleshoot their environment. It performs the following checks:

• Tool Verification: Checks for pyenv or mise in the system PATH.

• Network Reachability: Verifies connectivity to python.org.

• Permissions: Ensures the user has write access to the home directory for configuration and updates.

Testing:

• Ran pyvm doctor on [Your OS - e.g., Windows 11/Ubuntu].

• Verified that it correctly identifies missing network or missing tools.

[shreyasmene06]

This is exactly how the doctor command should be implemented - clean, simple, and properly integrated with the existing codebase. Great work!

• Single file change to existing cli.py
• Clean, readable implementation
• Good user feedback with colored output
• Checks all three requirements (tools, network, permissions)
• Single, well-described commit

Minor suggestions (non-blocking)

1. Add blank line before decorator (PEP 8 style):

        sys.exit(1)
@cli.command()  # <-- Add one more blank line above (should be 2 between functions)
def doctor():

2. Consider adding a simple test (optional, can be done in a follow-up):

def test_doctor_command(runner):
    result = runner.invoke(cli, ["doctor"])
    assert result.exit_code == 0
    assert "health check" in result.output.lower()

These are all minor - the implementation is solid. LGTM! 🎉

just make sure the workflow checks are passed too you can try them locally, check contributing.md

[saksham-stack]

I've changed what you requested please revies it once more. @shreyasmene06

[shreyasmene06]

Merged manually after resolving conflicts. The doctor command has been added to main.