fix(windows miner): run without tkinter (headless mode)

[sophiaeagent-beep]

Windows users sometimes hit a tkinter/Tcl error on minimal/embeddable Python installs.

This PR:

• Makes tkinter optional and auto-falls back to headless mode when missing
• Adds explicit CLI flags: --headless, --wallet, --node
• Updates miners README with the headless command

How to test:

• python miners/windows/rustchain_windows_miner.py --headless --wallet test_wallet --node https://50.28.86.131
• Or run without args on a Python that lacks tkinter and confirm it falls back to headless

Update:

• Updated miners/windows/rustchain_miner_setup.bat to detect missing tkinter and run the official Python installer with Include_tcltk=1 (and still documents --headless as fallback).