revert(readme): restore canonical README.adoc; remove runaway .md conversion

AsciiDoc is canonical here; the estate-wide 'convert -> Markdown' pass over-applied
the narrow boj-server/hyperpolymath .md rule. Restore README.adoc, remove README.md.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: hyperpolymath