docs: archive old DEVLOG iterations to reduce context size

Moved iterations 1-69 (plus superseded 70-76) to DEVLOG-archive.md.
DEVLOG.md reduced from 811 to ~190 lines, keeping only current-relevant
iterations 70-91.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: scari