Revamp HTML-to-Formatter tool: bug fixes, tests, UI overhaul

[gasharm]

Summary

• Bug fixes in HTML-to-JSON conversion: proper handling of <p>, <filepreview>, SVG attributes (viewBox, preserveAspectRatio, d), aria-* attributes, data-interception, and CSS shorthand properties
• Expanded test suite from 6 to 31 tests covering edge cases, SVG elements, nested structures, and CSS specificity
• UI overhaul: modernized three-pane layout (Code, Generated CF JSON, HTML Preview) with resizable drag edges, auto-convert on typing (300ms debounce), iframe-based isolated HTML preview, built-in example card, new app logo and favicon, and updated README

Test plan

• yarn test — 31 tests pass
• yarn build — builds successfully with no errors
• Visual check: HTML Preview renders responsively without CSS leakage from the app
• Visual check: JSON output generates correctly for the default example
• Visual check: Panel resizing works via drag edges between all sections
• Visual check: Copy button copies JSON to clipboard

🤖 Generated with Claude Code