Add advanced layout capabilities

[vitormattos]

Summary

• add advanced layout support for measured text, flex/block containers, clipping, vector decorations, and richer typography behaviors
• add XObject placement helpers and optional HTML context interpolation for template compilation
• expand documentation, integration scenarios, and mutation-focused regressions across layout, parser, PDF builder, and compiler paths

Validation

• docker compose run --rm php composer lint
• docker compose run --rm php composer phpmd
• docker compose run --rm php composer test:unit
• docker compose run --rm php vendor/bin/phpunit tests/Integration
• docker compose run --rm php composer performance:check (iterations=200 avg_ms=0.1554 peak_kb=0)
• docker compose run --rm php vendor-bin/mutation/vendor/infection/infection/bin/infection --threads=max (MSI 78%, Covered Code MSI 83%)