feat(viewer): support bounded multi-role comparison

[seekskyworld]

Summary

• extend Semantic Lens from two to a bounded maximum of four semantic kinds
• distinguish single-kind node inspection from multi-kind role comparison
• add temporary hover/focus previews for Upstream and Downstream controls; click/keyboard activation pins the authored state and URL
• preserve Escape/Clear, keyboard navigation, reduced-motion, embed, print, and export boundaries
• refresh all generated artifacts, gallery outputs, README proof, and canonical archify.zip

Issue

Closes #83

Verification

• node --test test/semantic-lens.test.mjs test/authored-reachability.test.mjs passes 8/8
• npm test passes 987/987 executed tests (1,018 total; 31 skipped)
• Existing two-kind direct relationship comparison remains unchanged
• Canonical SVG remains free of viewer-only lens/reachability state

[yunaremaia]

Closing this PR — the branch is conflicting and a cleaner implementation exists elsewhere. Will revisit with a fresh branch when capacity allows.