chore: remove abandoned CHANGELOG.md

CHANGELOG.md was created June 19, 2025 with the intent to document
notable changes following the Snowball Method principle. However, it
was abandoned after only 4 entries over a 24-day period (July 13, 2025).

Since then, 483 commits have been made with zero CHANGELOG updates,
proving the approach was unsustainable. The manual curation overhead
provided no value beyond what git commit history already captures through
structured commit messages.

The Snowball Method principle continues to thrive through:
- Living knowledge base (12 files actively reference it)
- knowledge/principles/snowball-method.md (recently enhanced with MLflow)
- Automated procedures and workflows (not manual documentation)

Stats:
- Active period: June 19 - July 13 (24 days)
- Total entries: 4 (~0.9% of commits during that period)
- Months abandoned: 3
- Lines removed: 35

Principle: subtraction-creates-value (removing manual process that
failed in practice)

Author: atxtechbro