docs: de-dup CHANGELOG/README per RSR standard (keep .adoc; port sponsor badge)

Keeps the maintained CHANGELOG.adoc, removes the stale v0.1.0 CHANGELOG.md stub
(verisimiser reversed — its .md is the richer/canonical one). Removes the
duplicate README.md, porting its sponsor badge into README.adoc so the rendered
GitHub page keeps it. RSR: no duplicate doc formats.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Mbq6yKF9RhFai6EQ7WqKhQ

Author: claude