vivliostyle.js

Fix Vivliostyle.js bugs found by WPT reftest and reftest-diff failures. Use when: investigating FAIL results from yarn test:reftest or yarn test:reftest-diff, comparing test vs reference render, fixing longstanding WPT failures or regressions, or working through grouped WPT issues such as #1915.

Resolve a Vivliostyle.js GitHub issue end-to-end. Use when: reproducing a bug, fixing an issue, creating test case from issue, verifying issue behavior, debugging rendering problems. Fetches issue content, creates an HTML test file, reproduces the bug visually with the VS Code integrated browser, and falls back to Chrome DevTools MCP when DevTools-specific diagnostics are needed.

Draft a conventional commit message in Markdown from the current changes. Use when: writing a commit message proposal, summarizing staged or unstaged changes, preparing a changelog-friendly commit title, or drafting a message for a GitHub issue fix. Produces text only and never runs git commit.