Add raw HTML runtime dependency parity report

[chubes4]

Summary

• Add an artifact-level source_reports.runtime_dependency_parity report for simple JavaScript DOM target dependencies.
• Detect getElementById, simple querySelector/querySelectorAll id/class selectors, simple attached events, and canvas 2d API usage for canvas targets.
• Compare those references against generated block markup and report missing DOM targets, with telemetry-like scripts downgraded to info.
• Preserve safe source ids as core block anchors so converted core blocks can retain runtime DOM targets where possible.

Tests

• composer test:canonical
• composer test
• Manual liquidbonsai fixture compile from /Users/chubes/Downloads/raw-html/saveweb2zip-com-liquidbonsai-com confirmed first-party #canvas warning and Netlify RUM info finding.

AI assistance

• AI assistance: Yes
• Tool(s): openai/gpt-5.5 via OpenCode
• Used for: Implementing the runtime dependency parity report, contract coverage, local verification, and PR drafting.