fix: preserve docs wordmark proportions

[abrichr]

Summary

• remove the SVG text-length constraints that compressed the OpenAdapt wordmark
• give the natural wordmark enough horizontal space in the Docs header
• replace brittle logo-copy assertions with a geometry contract

Validation

• python scripts/validate_docs.py
• python -m pytest tests/test_brand_styles.py -q
• python -m mkdocs build --strict
• desktop and mobile headless-Chrome visual checks
• git diff --check