Preserve runtime DOM targets in php transformer

[chubes4]

Summary

• Preserve runtime-targeted inline DOM nodes as bounded raw HTML instead of lossy empty group shells.
• Preserve runtime-targeted canvas elements in serialized block output while keeping runtime-island metadata.
• Add artifact parity coverage for first-party canvas scripts and empty inline runtime targets like loading/status spans.

Why

Static Site Importer imports that carry first-party runtime scripts can break when the transformer reports runtime targets as metadata but omits the actual DOM nodes from generated markup. Liquid Bonsai exposed two generic cases:

• document.getElementById('canvas').getContext('2d') needs a real <canvas id="canvas">.
• Dynamic status/loading spans like <span id="sync-dots"></span> need the exact runtime target to survive conversion.

Testing

• php php-transformer/tests/contract/run.php
• php php-transformer/tests/contract/finding-contract.php
• php php-transformer/tests/parity/run.php

AI assistance

• AI assistance: Yes
• Tool(s): openai/gpt-5.5 via OpenCode
• Used for: Diagnosing the runtime target preservation gap, drafting the transformer patch, adding regression fixtures, and running targeted verification.