dsteem Modernization Plan -Final Phase -7

Day 7: the short, satisfying one. typedoc 0.13 → 0.28 (an absurd 15-minor-version jump), drop the ugly sed post-processing the old Makefile needed to fix absolute paths in the generated HTML, and replace it all with a four-line typedoc.json. The API documentation regenerates cleanly with the modern layout. With this done, the modernization is feature-complete — every architectural change from the Phase 0 plan is in. All that's left is the release ceremony next week.