* Fix Biome lint violations and add Biome CI check
Biome was not configured to respect .gitignore, so ~92% of the 13,355
reported diagnostics came from gitignored build artifacts. Enable VCS
integration (useIgnoreFile), apply safe auto-fixes across the repo, fix
the remaining mechanical errors by hand, downgrade judgment-call a11y /
dangerouslySetInnerHTML rules to warnings, and add a 'biome ci' job to
the Lint workflow so violations block PRs going forward.
* Use an empty changeset (no behavior change, no release needed)
Nathan Rajlich