license: make the MIT grant explicit

[htayj]

Summary

• add the standard MIT license for Taylor Hardy's original contributions
• document the provenance and rights boundary of the ROM-derived VT220 glyph data
• document the NetHack screenshot and trademark boundaries
• include the license and third-party notices in release archives and installed packages
• align RPM metadata and package-content verification

The MIT grant is now explicit without purporting to relicense the historical DEC glyph designs, VT220 firmware, or VT100.net source image.

Verification

• make ci VERSION=license-test
• make nix-check
• shell syntax and staged-diff checks
• exact license and notice files verified in the source archive
• DEB, RPM, Arch, Gentoo, and Void staging payloads verified
• direct Arch and Void package builds completed

Closes #1